| 1. |
- Bergström, Ulf, et al.
(författare)
-
Workshop on Stickleback and Round Goby in the Baltic Sea (WKSTARGATE)
- 2022
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The aim of the Workshop on Stickleback and Round Goby in the Baltic Sea (WKSTARGATE) was to update, summarize and synthesize the current knowledge of both species with respect to their ecology and potential use in fisheries. Ongoing projects were presented in the mornings of the first two days to inform participants about current research in the respective countries (Annex 5). The group discussed ecological aspects that are relevant to fisheries, such as distribution and abundances, feeding ecology and behaviour. So far, no dedicated monitoring exists for either of the species. However, the Baltic International Acoustic Survey (BIAS), coordinated by ICES, has been used to estimate abundances and biomasses of pelagic stickleback in offshore areas across the Baltic, while the availability and quality of coastal data differs between countries, but is generally scarce. Even less current abundance information is available for round goby. It is only available for areas where it is already commercially exploited like Latvia.Most studies on the ecological impact of these species focus on trophic interactions, and its resulting competition. It became clear, that these ecological impacts depend on the abundance of the species and that the effects therefore vary on a temporal and spatial scale. Estimating the ecological impact of a stickleback or round goby fishery is therefore very speculative without reliable abundance data, why the group decided to describe the known impact of the species on the ecosystem.Landings of round goby increased significantly in Latvia during the last years, while stickleback landings decreased over the last five decades but most recently show a slight increase. A targeted round goby fishery exists in Latvian waters, while the stickleback is solely taken as bycatch in all Baltic countries. Both fisheries are currently unmanaged and, with the exception of round goby fishery in Latvia, unregulated. In Latvia the round goby fishery is regulated by effort, to reduce the bycatch of native species. Furthermore, Latvia has initiated work towards a stock assessment of round goby. Efforts for a Baltic-wide stickleback assessment have been undertaken by Sweden, and both, Sweden and Denmark are taking first steps towards a full analytical stock assessment.
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| 2. |
- Blenckner, Thorsten, et al.
(författare)
-
Preface
- 2011
-
Ingår i: Hydrobiologia. - : Springer Science and Business Media LLC. - 0018-8158 .- 1573-5117. ; 660:1, s. 1-2
-
Tidskriftsartikel (refereegranskat)
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| 3. |
- Bryhn, Andreas, et al.
(författare)
-
Fisk- och skaldjursbestånd i hav och sötvatten 2019 : Resursöversikt
- 2020
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Fisken i havet är en resurs som rör sig fritt över nationella gränser. EU har därför en gemensam fiskeripolitik (GFP). Många arter som är viktiga för Sverige regleras inte i GFP och förvaltas därför nationellt.Denna rapport syftar till att:beskriva utvecklingen av fiskeripolitikenförklara den nuvarande politikens mål och regelverk och dess relation till mål och regler på miljöområdetförklara politikens nationella genomförande och det nationella handlingsutrymmetexemplifiera hur Havs- och vattenmyndigheten arbetat med att reglera fisket.
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| 4. |
- Edsman, Lennart, et al.
(författare)
-
A global-scale screening of non-native aquatic organisms to identify potentially invasive species under current and future climate conditions
- 2021
-
Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 788
-
Tidskriftsartikel (refereegranskat)abstract
- The threat posed by invasive non-native species worldwide requires a global approach to identify which introduced species are likely to pose an elevated risk of impact to native species and ecosystems. To inform policy, stakeholders and management decisions on global threats to aquatic ecosystems, 195 assessors representing 120 risk assessment areas across all six inhabited continents screened 819 non-native species from 15 groups of aquatic organisms (freshwater, brackish, marine plants and animals) using the Aquatic Species Invasiveness Screening Kit. This multi-lingual decision-support tool for the risk screening of aquatic organisms provides assessors with risk scores for a species under current and future climate change conditions that, following a statistically based calibration, permits the accurate classification of species into high-, medium-and low-risk categories under current and predicted climate conditions. The 1730 screenings undertaken encompassed wide geographical areas (regions, political entities, parts thereof, water bodies, river basins, lake drainage basins, and marine regions), which permitted thresholds to be identified for almost all aquatic organismal groups screened as well as for tropical, temperate and continental climate classes, and for tropical and temperate marine ecoregions. In total, 33 species were identified as posing a & lsquo;very high risk & rsquo; of being or becoming invasive, and the scores of several of these species under current climate increased under future climate conditions, primarily due to their wide thermal tolerances. The risk thresholds determined for taxonomic groups and climate zones provide a basis against which area-specific or climate-based calibrated thresholds may be interpreted. In turn, the risk rankings help decision-makers identify which species require an immediate & lsquo;rapid & rsquo; management action (e.g. eradication, control) to avoid or mitigate adverse impacts, which require a full risk assessment, and which are to be restricted or banned with regard to importation and/or sale as ornamental or aquarium/fishery enhancement.(c) 2021 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).
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| 5. |
- Florin, Ann-Britt, et al.
(författare)
-
Abundance and distribution of round goby (Neogobius melanostomus)
- 2018
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The round goby has established in all Baltic Sea sub-basins and is continuously increasing its range and abundance in recently colonized habitats. The species has become the predominant fish species in many coastal areas and poses strong predatory pressure essentially on epibenthic mollusks. It has also become an important prey species in areas where it is numerous, with signs of individual-level benefits for some piscivorous fish.
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| 6. |
- Florin, Ann-Britt, et al.
(författare)
-
Status and Trends in the Rate of Introduction of Marine Non-Indigenous Species in European Seas
- 2022
-
Ingår i: Diversity. - : MDPI AG. - 1424-2818. ; 14
-
Tidskriftsartikel (refereegranskat)abstract
- Invasive alien species are a major worldwide driver of biodiversity change. The current study lists verified records of non-indigenous species (NIS) in European marine waters until 2020, with the purpose of establishing a baseline, assessing trends, and discussing appropriate threshold values for good environmental status (GES) according to the relevant European legislation. All NIS records were verified by national experts and trends are presented in six-year assessment periods from 1970 to 2020 according to the European Union Marine Strategy Framework Directive. Altogether, 874 NIS have been introduced to European marine waters until 2020 with the Mediterranean Sea and North-East Atlantic Ocean hosting most of the introductions. Overall, the number of new introductions has steadily increased since 2000. The annual rate of new introductions reached 21 new NIS in European seas within the last six-year assessment period (2012–2017). This increase is likely due to increased human activities and research efforts that have intensified during the early 21st century within European Seas. As Europe seas are not environmentally, nor geographically homogenous, the setting of threshold values for assessing GES requires regional expertise. Further, once management measures are operational, pathway-specific threshold values would enable assessing the effectiveness of such measures.
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| 7. |
- Goedkoop, Willem, et al.
(författare)
-
Retention of N and P by zebra mussels (Dreissena polymorpha Pallas) and its quantitative role in the nutrient budget of eutrophic Lake Ekoln, Sweden
- 2011
-
Ingår i: Biological Invasions. - : Springer Science and Business Media LLC. - 1387-3547 .- 1573-1464. ; 13, s. 1077-1086
-
Tidskriftsartikel (refereegranskat)abstract
- We quantified cover, population densities, size distribution and biomass of zebra mussels along 7 transects in eutrophic Lake Ekoln (Sweden). We also analyzed the elemental (C, N, P) composition of zebra mussel soft tissue and computed their retention rates of N and P their quantitative role in the lake's nutrient budget. We hypothesized that zebra mussels play an important role in the nutrient budget of the lake and speculate that the successive harvesting of cultured mussels could contribute to the lake's rate of recovery from cultural eutrophication. At depths exceeding 5 m, mussels covered consistently less than 5% or were absent. Similarly, mean densities were 3,158 +/- A 2,143 ind m(-2) between 2 and 4 m, but rapidly declined at larger depths. Calculated clearance rates averaged 19.4 +/- A 2.3 km(3) y(-1), implying the entire lake is filtered every 8-10 days. Concentrations of N and P in mussel soft tissue averaged 100.9 +/- A 1.5 mg N g(-1) DW and 9.3 +/- A 0.2 mg P g(-1) DW. The lake population was estimated to 22.2 +/- A 2.6 x 10(10) mussels, corresponding to a standing stock biomass of 362 +/- A 42 ton DW, or conservative estimates of 36.6 +/- A 4.3 ton N and 3.4 +/- A 0.4 ton P. Assuming a life span of 2-3 years gives a retention estimate of 1.2-1.8 ton P y(-1) by mussels, corresponding to 50-77% of the annual P influx from Uppsala sewage treatment plant to the lake. Similarly, annual N-retention by zebra mussels makes up 13-20 ton N y(-1), largely equaling the annual N-deposition from atmospheric sources on the lake's surface. These retention rates correspond to only a few percent of the annual P-load from agricultural sources, but we argue that the quantitative role of zebra mussels in nutrient budgets is much larger if these budgets are adjusted for the bias introduced by coarse estimates of N and P pools that include a large share of refractory P.
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| 8. |
- Königson, Sara, et al.
(författare)
-
Effects of fishery and environmental factors on a novel multispecies pot targeting European lobster (Homarus gammarus), Atlantic cod (Gadus morhua) and edible crab (Cancer pagurus)
- 2022
-
Ingår i: Frontiers in marine science. - : Frontiers Media SA. - 2296-7745. ; 9
-
Tidskriftsartikel (refereegranskat)abstract
- Small-scale fisheries along the Swedish west coast are often operated by using small vessels, targeting multiple species by means of pots and gillnets. Fisheries using pots targeting shellfish such as European lobster (Homarus gammarus), and edible crab (Cancer pagurus) along the Swedish west coast have a relatively high economic value. However, gillnet fisheries targeting demersal fish are currently diminishing primarily due to depleted fish stocks and increased seal depredation. Small-scale fisheries are considered sustainable fisheries due to the use of selective gears and low energy consumption. To be able to retain and promote a sustainable small-scale fishery, there is a need to develop an economically viable fishery, where selective, seal-safe and sustainable gear is utilized. One potential way forward could be to develop a pot to be used for multiple target species traditionally caught in pots and gillnets. Since both shellfish and cod (Gadus morhua) can be caught in pots, the objective of this work was to develop a multispecies pot targeting lobster, edible crab and cod. Seven multi-species pots were developed and tested off the west coast of Sweden between 2015 and 2017. The catch rate, defined as catch per pot per day (CPUE) of lobster, edible crab and cod, was evaluated taking into regard fisheries-related variables such as pot type, bait, soak time, seal damage and abundance of species in the pot. The relative CPUE of lobster and cod was highest in larger pots with two chambers and three open entrances. The highest CPUE for lobster was 0.24 individuals per pot and the highest CPUE for cod was 0.17 individuals per pot. Pots with entrances equipped with funnels, preventing cod from escaping, also had a high cod CPUE (0.23 individuals per). The CPUE of crabs was not affected by pot type. For cod, lobster and crab, the CPUE significantly decreased with increasing soak time. Seal damage only occurred when cod were trapped in the pots and the CPUE of cod was higher in pots subjected to seal damage, indicating that seals raid pots specifically when cods are trapped inside.
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| 9. |
- Königson, Sara, et al.
(författare)
-
Will harbor porpoises (Phocoena phocoena) be deterred by a pinger that cannot be used as a "dinner bell" by seals?
- 2022
-
Ingår i: Marine mammal science. - : WILEY. - 0824-0469 .- 1748-7692. ; 38:2, s. 469-485
-
Tidskriftsartikel (refereegranskat)abstract
- A measure proven successful in mitigating harbor porpoise bycatch, is the use of acoustic deterrents, i.e., pingers. However, most pingers are audible to seals. This may lead to seals associating pinger sounds with easily accessible food, leading to increased depredation, damage, and bycatch. In this study we tested if an experimental pinger, emitting sounds over 30 hr ON/OFF cycles, with low frequency components potentially audible to seals only at close distances, would effectively deter harbor porpoises. The porpoise response was measured by logging echolocation clicks, using C-POD click detectors, moored at different distances from the pinger. In addition, we calculated the theoretical pinger detection range for seals. Results showed that the pinger had a significant negative effect on the porpoise click activity logged at 0 m and 100 m distance but not at 400 m from the pinger. During pinger ON periods, we found no significant increase in echolocation over consecutive days of the study, suggesting no habituation to pinger sounds. Our theoretical detection distances indicate that seals can only detect the pinger at close distances, preventing seals from using this pinger as a "dinner bell."
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| 10. |
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| 11. |
- Naddafi, Rahmat
(författare)
-
Application of stable isotopes of carbon (13δC) and nitrogen (15δN) in assessment of Gorgan Bay fish dynamic in Golestan province
- 2021
-
Ingår i: Journal of Applied Ichthyological Research. - 2423-6349. ; 8, s. 46-53
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Gorgan Bay and the southeastern coasts of the Caspian Sea in the Golestan Province are important biological and fisheries areas, while in recent years, they have been heavily contaminated. In present study, the dynamic of fishes, using stable nitrogen and carbon isotopes was evaluated to determine the diet and its trophic status, which can accurately chart the ecosystem's biological conditions. Accordingly, in September-October 2015 at 5 ecological stations, sampling of prephytones, macrophytes, macro invertebrates and fish, were taken and dominant species were subjected to isotope analyzes using the EA-IRMS device. The results of the nitrogen15 and carbon-13 isotopes indicate an imbalance in ecosystem conditions that alters the diet of the organisms and reduces the efficiency of the food web. The main factors of pressure on the ecosystem, the closure of the main channels of the sea to the bay, the entry of various pollutants into the ecosystem and weak physiography of Gorgan Bay, were determined.
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| 12. |
- Naddafi, Rahmat
(författare)
-
Composition of fish larvae in the central creeks of Bushehr province, Persian Gulf in 2013-2014
- 2015
-
Ingår i: Journal of Applied Ichthyological Research. - 2423-6349. ; 3, s. 1-18
-
Tidskriftsartikel (refereegranskat)abstract
- This study was carried out to identify the taxonomic composition of fish larvae collected bimonthly in waters of Bushehr to Genaveh in six stations (Five creeks: Shif, Lashkari, Ramleh, Farakeh, Dubbeh, and one station in the seashore) in norhtern Persian Gulf, Iran, from June 2013 to April 2014. Fish larvae were sampled usinga Bongo-net (diameter, 60 cm; mesh size, 300 µm).A total of 21440 fish larvae representing 30 families (which included two subfamilies, eightgenuses, nine species and eight types), one group to the levels of order and two types were recognised. The identified taxa were: Apogonidae, Blenniidae, Callionymidae, Carangidae, Clupeidae, Cynoglossidae, Diodontidae, Engraulidae, Gerreidae, Gobiidae, Haemulidae, Hemiramphidae, Leiognathidae, Mugilidae, Mullidae, Nemipteridae, Pegasidae, Platycephalidae, Scatophagidae, Sciaenidae, Scombridae, Sillaginidae, Soleidae, Sparidae, Sphyraenidae, Synanceidae, Syngnathidae, Terapontidae, Triacanthidae, Tripterygiidae, and Tetraodontiformes. Among them, Soledae (including 6 types) and Gobiidae (including 3 types) were the most diverse families. What is more,Pegasus volitans(Pegasidae),Cyclichthys orbicularis(Diodontidae),Trachurus indicus(Carangidae), andHippichthys penicillus(Syngnathidae) were reported for the first time in Iranian waters.
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| 13. |
- Naddafi, Rahmat, et al.
(författare)
-
Developing management goals and associated assessment methods for Sweden’s nationally managed fish stocks : a project synthesis
- 2023
-
Rapport (refereegranskat)abstract
- This report summarizes and synthesizes results from the Swedish Agency of Marine and Water Management (SwAM, or HaV) funded project “Förvaltningsmål för nationella arter (Management goals for nationally managed species)”. The objectives of the project have been to promote the development of management goals and associated status assessment methods and indicators, as well as reference points, for some nationally managed fish stocks both in coastal as well as freshwater areas. The report focusses largely on species and stocks that can be defined as data-poor. Such stocks are characterised by marked limitations in data availability and/or resources allocated to detailed analytical stock projections. Data-poor stocks also often lack carefully formulated management goals and associated methods and indicators for assessing stock status. In this report, we provide an overview of potential assessment methods and indicators and try to synthesise how they work and what the strengths and weaknesses are by applying them to selected data poor stocks such as pikeperch, pike, whitefish, and vendace. We also discuss how they relate to different potential management goals and provide recommendations for their application. We grouped the indicators and assessment methods by the three categories that are now used in the yearly status assessment framework provided by SLU Aqua (Resursöversikten/Fiskbarometern) – i) mortality, ii) abundance/biomass and iii) size/age structure. The results are also described for these three main categories of assessment indicators. Included is also a status report from a size- and age-based population dynamics model (Stock Synthesis 3) that is being developed for pikeperch in Lake Hjälmaren.An important experience from the project is that to improve the assessment methods for Swedish national fish stocks, it is important that managers develop both general as well as more detailed quantitative goals for the individual stocks. This should ideally be conducted in various forms of collaboration with the main stakeholders and scientists involved with assessment as participatory processes foster legitimacy. Carefully articulated management goals, which are possible to translate into quantitative targets, will facilitate the development of various approaches and methods to monitor stock statuses. Given the strong and complex interactions of fish and their environments it is also important to consider other pressures than fisheries when developing indicators and assessment methods.Our synthesis highlights a number of areas where the assessment of data-poor stocks can be improved:1. Apply precautionary principles for data-limited stocks, particularly ones that are known to be vulnerable to exploitation.2. Tailor approaches to how fisheries are managed in Sweden. Swedish nationally managed fish stocks are not managed by quotas (with one exception, vendace in the Bothnian Bay) and do not aim for maximum sustainable yield. Instead, the coastal and inland fisheries are managed by regulating the effort in the small-scale commercial fisheries (number of fishers/licenses and amount of gear). Regulation of recreational and subsistence fisheries effort, in terms of licenses or number of fishers) is not applied, nor possible since the fisheries is lacking obligatory notification and reporting systems. All national fisheries, however, are regulated by various technical measures (closed areas, size-limits, bag-limits, gear restrictions etc). Thus, goals and assessment methods that result in harvest limits or quota recommendations expressed in e.g. biomass/numbers are difficult to use as basis for management. Instead, there is a need for alternative management goals and associated assessment methods.3. Use best practice methods and indicators and adapt as scientific knowledge is developed. Data-limited methods are developing rapidly, and new methods/approaches are proposed in the scientific literature every year. It is thus important to be updated on the most recent developments. 4. Clearly describe limitations/assumptions of methods used. It is important to be aware of and critically evaluate the assumptions underlying the analyses, and to carefully communicate uncertainty together with the stock status assessment.5. Be particularly careful with low sample numbers. Many indicators and methods can be applied also on small sample sizes, however, the accuracy and precision of the estimates risk being low in such cases.6. Accept that there is no "gold standard" for fisheries assessment. Each case study is unique and needs to be balanced against data availability, local needs and other important factors. This also means that analysts need to be careful when using generic reference levels or “borrowing” data from other stocks.7. If possible, use several different methods/indicators. Although several indicators aim to measure similar aspects of the stock, small methodological differences can support the overall interpretation of individual indicator values. It is particularly important to incorporate many aspects and indicators (size/age/abundance/mortality) in order to produce a balanced assessment.8. Develop means of communication. Indicators and goals should be easy to understand. However, interpretation of results from multi-indicator frameworks can be challenging. There is thus a need for finding ways of communication that can convey complicated results in a simple-to-understand manner.9. For details on additional improvements, we refer the reader to the sub-header “recommendations for the future” found under each chapter.The implementation of Stock Synthesis for pikeperch in Lake Hjälmaren showed that it is possible to develop a more ambitious and detailed stock assessment model for a relatively data-poor stock. The model results partly support earlier interpretations of the development of the stock and the importance of the changes in regulations in 2001 (increased minimum size, increased mesh size and reduced mortality of undersized pikeperch). Before the model can be implemented and used for practical management, a number of actions for improvement are needed, which are highlighted in the relevant chapter. The most important next step is establishing management goals and reference levels for this stock. We recommend that such a dialogue is initiated by managers. The fisheries management goals should consider both biomass, fisheries mortality and size-based targets.To conclude, we stress the importance of improving all ongoing aspects related to the assessments of data-poor Swedish stocks. Strong local stocks and sustainable fisheries are vital for a variety of fisheries-related businesses and practices, particularly in rural areas, providing economical and societal value. Fishes also have important roles in aquatic food-webs and it is important that ecological values are managed wisely in order to reach targets for water quality, ecosystem structure and diversity. Given the strong and complex interactions of fish and their environments it is also important to consider other pressures than fisheries when developing indicators and assessment methods.
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| 14. |
- Naddafi, Rahmat
(författare)
-
Diversity and spatial distribution patterns of the benthic macrofauna communities in the southeast of the Caspian Sea (Golestan Province- Iran) in relation to environmental conditions
- 2020
-
Ingår i: Iranian Journal Of Fisheries Sciences. - 1562-2916. ; 19, s. 525-540
-
Tidskriftsartikel (refereegranskat)abstract
- Biodiversity and structure of the benthic macrofauna communities were studied in the southeast the Caspian Sea (Golestan Province - Iran) during one year from October 2014 to September 2015. Seasonal samplings were done at 6 stations in 3 transects. Depth, temperature, salinity, pH, E.C., total organic matter and grain size were measured. More than 4,037 individuals belonging to five orders, Polychaeta, Oligochaeta, Bivalvia, Diptera and Amphipoda, and eight families including Nereididae, Spionidae, Amphartidae, Tubificidae, Smelidae, Cardiidae, Chironomidae and Gammaridae were identified. In terms of total individuals, Streblospio gynobranchiata, Hypania invalida and Cerastoderma lamarcki, were the most abundant species, and Polychaeta were dominant in the research region. The highest density of all species was observed in autumn (1515 ind m(2)) and the lowest was observed in summer (698 ind m(2)). The maximum diversity, richness, and evenness were 1.36, 0.6 and 0.98, respectively. The results of distance-based redundancy analysis (db-RDA) showed that environmental factors such as salinity, depth and substrate type were all important in detecting the distribution pattern of macrobenthic species in the research region. The dominant species, S. gynobranchiata, was distributed in the areas with smaller grain size and higher TOM and muddy sediments and had the most correlation with salinity, temperature, pH and E.C. Species such as T fraseri. H. invalida and P. robustoides showed more dependency on TOM and mud factors in the spring and summer, while their dependency became lower in autumn and winter. Abra ovate was less influenced by all factors except the substrate.
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| 15. |
- Naddafi, Rahmat
(författare)
-
Diversity, distribution, and abundance patterns of ichthyoplankton assemblages in some inlets of the northern Persian Gulf
- 2021
-
Ingår i: Journal of Sea Research. - : Elsevier BV. - 1385-1101 .- 1873-1414. ; 167
-
Tidskriftsartikel (refereegranskat)abstract
- Distribution patterns of fish at early life stages can have profound effects on their development and survival. Here, diversity, distribution, and abundance patterns of ichthyoplankton assemblages were investigated in some inlets of the northern Persian Gulf during 2013-2014. A total of 21,440 fish larvae belonging to 30 families were identified, with Clupeidae, Gobiidae and Sillaginidae being the most dominant families. Spatial segregation of stations and species-environmental ordination patterns were observed according to multivariate analyses. Two larger inlets and one which had freshwater input supported higher abundances of fish larvae, whereas the smallest inlet and the sea station were dominated by fish eggs. The highest and the lowest abundances of ichthyoplankton were observed in April and December, respectively. Our results suggest that there are temporal and spatial variations in ichthyoplankton assemblages of the northern Persian Gulf. Both generalized linear mixed model and distance-based redundancy analysis revealed that water temperature, transparency, and depth were the key variables affecting the larval fish abundance. The results of this study provide valuable insights into fish larval ecology in shallow subtropical estuaries and inlets and help to explore how fish larvae respond to space-time environmental conditions.
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| 16. |
- Naddafi, Rahmat
(författare)
-
Does differential predation explain the replacement of zebra by quagga mussels?
- 2014
-
Ingår i: Freshwater Science. - : University of Chicago Press. - 2161-9549 .- 2161-9565. ; 33, s. 895-903
-
Tidskriftsartikel (refereegranskat)abstract
- We examined the hypothesis that direct predation is part of the explanation for the displacement of zebra (Dreissena polymorpha) by quagga mussels (Dreissena rostriformis bugensis) in North America. We investigated selectivity and feeding rates by 3 predators (Round Goby, Pumpkinseed Sunfish, rusty crayfish) using 2 or 3 size classes of predators feeding on different size classes of both mussel species. Round Goby, the predator with a long evolutionary history with dreissenids, consumed a larger range of dreissenid sizes than the other 2 predators. Pumpkinseed Sunfish did not show a preference for either mussel species, but both rusty crayfish and gobies preferred quagga mussels over zebra mussels. The size of mussels vulnerable to these predators increased with predator size, but all predators preferred the smallest mussels (4-8 mm). Medium (105-125 mm) and large (135-155 mm) Round Gobies consumed the largest size class (16-20 mm) of quagga mussels, but only large Round Gobies were able to consume 16-20-mm zebra mussels. Crayfish consumed a higher number of quagga than zebra mussels in both the 8-12-mm and 12-16-mm size classes. Large Pumpkinseed Sunfish (170 185 mm) were able to consume the largest size class of quagga but not zebra mussels. Our results do not support direct predation as the cause for quagga mussels replacing zebra mussels. However, predation may affect mussel size structure because small mussels were more vulnerable to predation than larger mussels.
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| 17. |
- Naddafi, Rahmat, et al.
(författare)
-
Effects of the zebra mussel, an exotic freshwater species, on seston stoichiometry
- 2008
-
Ingår i: Limnology and Oceanography. - : American Society of Limnology and Oceanography. - 0024-3590 .- 1939-5590. ; 53:5, s. 1973-1987
-
Tidskriftsartikel (refereegranskat)abstract
- We examined the effect of the zebra mussel, Dreissena polymorpha, an exotic species, on seston stoichiometry by conducting laboratory experiments in which we varied nutrient composition of seston and mussels over time. Zebra mussels altered the stoichiometry of seston through removal of particulate organic nutrients and changed the stoichiometry of the dissolved nutrient pool through nutrient excretion. Grazers had stronger effects on carbon : phosphorus (C : P) and nitrogen (N) : P ratios than on the C:N ratio of seston. Elemental residence time in tissue and high mass-specific nutrient excretion by small mussels caused small mussels to be more efficient nutrient recyclers than larger mussels. Zebra mussels reduced P availability through enhancing C: P and N: P molar ratios of seston during the period extending from June to August, when P was limited in the lake, and increased the C:N molar ratio of seston in June, when N was at the minimum level in the lake. C: P and N: P molar ratios for zebra mussel tissue were higher in August and somewhat in September than in all other months. N was retained more efficiently than P in Dreissena tissue. Nutrient mass-specific uptake rate was higher than excretion rate by zebra mussels.
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| 18. |
- Naddafi, Rahmat
(författare)
-
Genetic diversity of Dussumieria acuta (Valenciennes, 1847) in Persian Gulf and Oman sea (coast of the Hormozgan province) using cytochrome oxidase subunit I gene (COI)
- 2021
-
Ingår i: Journal of Applied Ichthyological Research. - 2423-6349. ; 8, s. 12-18
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In this study 12 specimens were collected from Bandar Jask, Qeshm Island and Bandare Lengeh in Hormozgan Province. DNA extraction was performed using Phenol-Chloroform method. A partial DNA sequence of Cytochrome oxidase subunit I gene (COI) was used to evaluate genetic diversity. The sequence of Cytochrome oxidase subunit I gene was done using specific primers designed based on sequences registered in NCBI GenBank. The diversity of 619 bp of COI was estimated. Gene sequencing of samples were compared with using MEGA5 and Bioedit7 software. Also, polymorphism or haplotype frequency was evaluated using dnaSp7 software. Results showed that there was low genetic distance equals to among all population and 9 haplotypes among samples were determined.
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| 19. |
- Naddafi, Rahmat, et al.
(författare)
-
Improving assessments of coastal ecosystems – Adjusting coastal fish indicators to variation in ambient environmental factors
- 2022
-
Ingår i: Ecological Indicators. - : Elsevier BV. - 1470-160X .- 1872-7034. ; 145
-
Tidskriftsartikel (refereegranskat)abstract
- The application of ecological indictors for assessing the environmental status of ecosystems play an important role for effective management. However, natural variability may limit the indicators’ ability to provide relevant information about anthropogenic pressures and guide management action. Coastal fish species are not only a resource for commercial and recreational fisheries but also key ecosystem components in the Baltic Sea, and is therefore used as management objectives within the EU Marine Strategy Framework Directive and the HELCOM Baltic Sea Action Plan. A challenge, however, is that the distribution and abundance of coastal fish populations in Baltic Sea is also influenced by spatial and temporal variation in ambient environmental factors. Here, using 16 years of monitoring data, over a latitudinal range of 56 – 66°N along the Swedish Baltic Sea coast, we evaluated the effect of variability in water temperature and depth, and wave exposure for three indicators of environmental status assessment in the Baltic Sea: Abundance of perch, Abundance of Cyprinids, and Abundance of Piscivores. Generalized linear mixed models (GLMM) revealed an overall positive linear relationship between water temperature for all indicators, and overall negative linear relationships to depth and wave exposure. When adjusting indicator values using the parameter estimates from the GLMM models, the variability and 95 % confidence interval for all three indicators were reduced. The adjustment, however, did not have a strong impact on the assessment of the ecological state of the indicator. Our results suggest that adjusting coastal fish indicators to variation in local ambient environmental factors will increase their precision, and hence, the confidence in the assessment of environmental status.
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| 20. |
- Naddafi, Rahmat
(författare)
-
Invasive European frogbit (Hydrocharis morsus-ranae L.) in North America: an updated review 2003-16
- 2018
-
Ingår i: Journal of Plant Ecology. - : Oxford University Press (OUP). - 1752-9921 .- 1752-993X. ; 11, s. 17-25
-
Forskningsöversikt (refereegranskat)abstract
- AimsEuropean frogbit (Hydrocharis morsus-ranae L.) is an aquatic plant originating from Europe that has emerged as an invasive species, spreading in the USA and Canada since it was first brought to North America in 1932. It can now be found in many water bodies, from small ponds and long rivers to large lakes such as Lake Ontario and Lake Erie. The continuous spread of this species indicates its success as an invasive species despite legislative attempts to limit its distribution. Catling et al. (Catling PM, Miltrow G, Haber E, et al. (2003) The biology of Canadian weeds. 124. Hydrocharis morsus-ranae L. Can J Plant Sci 83:1001-16) wrote a thorough review about this invasive species in North America. Our review aims for a compilation of the most recent available data and recent studies on H. morsus-ranae L. and focuses primarily on its environmental uses, ecological impacts and management. The purpose of this review is to offer an organized and updated report on European frogbit that can be used towards future studies with the goal of eradicating this invasive species and providing insights on management of other invasive plants.Important FindingsOur findings reveal that European forgbit's ecological effects on other species and the invaded environment were shown to be less harmful than previously feared. European frogbit had negative impacts on native plants and reduced dissolved oxygen concentration. However, water chemistry, phytoplankton and zooplankton communities were actually not affected by European frogbit. For fungi, bacteria and macroinvertebrates, studies have showed complex and sometimes conflicting results. We also specifically discussed the new method to control this species using shading and the more recent studies on biological control. Shading with a shade cloth has been shown to effectively remove European frogbit and had minor environmental effects. However, using biological control to combat the spread of the invasive frogbit seems not as successful as we wished.
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| 21. |
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| 22. |
- Naddafi, Rahmat
(författare)
-
Marine Strategy Framework Directive- Descriptor 2, Non-Indigenous Species : delivering solid recommendations for setting threshold values for non-indigenous species pressure on European seas
- 2021
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Marine Non-Indigenous Species (NIS)are animals and plants introduced accidently or deliberately into the European seas, originating from other seas of the globe. About 800 marine non-indigenous species (NIS)currently occurin the European Union national marine waters, several of which have negative impacts on marine ecosystem services and biodiversity. Under the Marine Strategy Framework Directive (MSFD) Descriptor 2 (D2), EU Member States(MSs)need toconsider NIS in their marine management strategies. The Descriptor D2 includes one primary criterion (D2C1: new NIS introductions),and two secondary criteria (D2C2and D2C3). The D2 implementation is characterized by a number of issues and uncertaintieswhich can beapplicable to the Descriptor level (e.g. geographical unit of assessment, assessment period, phytoplanktonic, parasitic, oligohaline NIS, etc.), to the primary criterion D2C1 level (e.g. threshold values, cryptogenic, questionable species, etc), and to the secondary criteria D2C2 and D2C3. The current report tackles these issues and provides practical recommendations aiming at a smoother and more efficient implementation of D2 and its criteria at EU level. They constitute a solid operational output whichcan result in more comparable D2 assessments among MSsand MSFD regions/subregions. When it comes to the policy-side, the current report callsfor a number of different categories of NIS to be reported in D2 assessments, pointing the need for the species to be labelled/categorised appropriately in the MSFD reporting by the MSs.These suggestions are proposed to be communicated to the MSFD WorkingGroup of Good Environmental Status (GES)and subsequently to the Marine Strategy Coordination Group (MSCG) of MSFD. Moreover, they can serve as an input for revising the Art. 8 Guidelines.
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| 23. |
- Naddafi, Rahmat, et al.
(författare)
-
Non-indigenous species refined national baseline inventories: A synthesis in the context of the European Union's Marine Strategy Framework Directive
- 2019
-
Ingår i: Marine Pollution Bulletin. - : Elsevier BV. - 0025-326X .- 1879-3363. ; 145, s. 429-435
-
Forskningsöversikt (refereegranskat)abstract
- Refined baseline inventories of non-indigenous species (NIS) are set per European Union Member State (MS), in the context of the Marine Strategy Framework Directive (MSFD). The inventories are based on the initial assessment of the MSFD (2012) and the updated data of the European Alien Species Information Network, in collaboration with NIS experts appointed by the MSs. The analysis revealed that a large number of NIS was not reported from the initial assessments. Moreover, several NIS initially listed are currently considered as native in Europe or were proven to be historical misreportings. The refined baseline inventories constitute a milestone for the MSFD Descriptor 2 implementation, providing an improved basis for reporting new NIS introductions, facilitating the MSFD D2 assessment. In addition, the inventories can help MSs in the establishment of monitoring systems of targeted NIS, and foster cooperation on monitoring of NIS across or within shared marine subregions.
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| 24. |
- Naddafi, Rahmat, et al.
(författare)
-
Non-lethal predator effects on the feeding rate and prey selection of the exotic zebra mussel (Dreissena polymorpha)
- 2007
-
Ingår i: Oikos. - 0030-1299 .- 1600-0706. ; 116:8, s. 1289-1298
-
Tidskriftsartikel (refereegranskat)abstract
- Predators may induce changes in prey feeding that indirectly influence both the impact of prey on resource abundances and their interactions with other species in their community. We evaluated whether clearance and excretion (faeces plus pseudofaeces) of phytoplankton by zebra mussels were affected by the presence of predatory cues from roach (Rutilus rutilus) and signal crayfish (Pasifastacus leniusculus). We found that non-lethal effects of predators can alter zebra mussel clearance rate and thus the impact of zebra mussels on phytoplankton. Risk cues released by both predators had similar negative effects on clearance rate of zebra mussels and cascading positive indirect effects on phytoplankton resources. Predation risk had a stronger effect on zebra mussels' clearance rate of cyanobacteria and diatoms than cryptophytes and chrysophytes. The presence of predators did not significantly affect the rate at which zebra mussels expelled and excreted phytoplankton, although there was a tendency for more chlorophyll to be expelled and excreted in the presence of predators. Our results contribute to the growing evidence that predators indirectly affect resource dynamics and food web structure through their non-lethal effects on consumers. Our results suggest that exotic species such as zebra mussels can show behavioural responses to both native (e.g., roach) and exotic (e.g., crayfish) predators.
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| 25. |
- Naddafi, Rahmat, et al.
(författare)
-
Physical and chemical properties determine zebra mussel invasion success in lakes
- 2011
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Ingår i: Hydrobiologia. - : Springer Science and Business Media LLC. - 0018-8158 .- 1573-5117. ; 669:1, s. 227-236
-
Tidskriftsartikel (refereegranskat)abstract
- To address the question whether the abundance of an invasive species can be explained by physical and chemical properties of the invaded ecosystems, we gathered density data of invasive zebra mussels and the physical and chemical data of ecosystems they invaded. We assembled published data from 55 European and 13 North American lakes and developed a model for zebra mussel density using a generalized additive model (GAM) approach. Our model revealed that the joint effect of surface area, total phosphorus and calcium concentrations explained 62% of the variation in Dreissena density. Our study indicates that large and less productive North American lakes can support larger local populations of zebra mussels. Our results suggest that the proliferation of an exotic species in an area can partially be explained by physical and chemical properties of the recipient environment.
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| 26. |
- Naddafi, Rahmat, et al.
(författare)
-
Predation and physical environment structure the density and population size structure of zebra mussels
- 2010
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Ingår i: Journal of The North American Benthological Society. - : University of Chicago Press. - 0887-3593 .- 1937-237X. ; 29:2, s. 444-453
-
Tidskriftsartikel (refereegranskat)abstract
- The zebra mussel (Dreissena polymorpha) provides one example of successful invaders in novel environments. However, little attention has been devoted to exploring the factors regulating zebra mussel density and population size structure at the local scale. We tested effects of physicochemical factors and fish predation on the density of zebra mussels at several sites and between years in a natural lake. Water depth and roach (Rutilus rutilus) density were the most important variables affecting local zebra mussel density. Substrate was also an important factor but affected Dreissena density only at the shallowest depth examined (2 m), which also supported a large population of the mussels. Mean shell length of Dreissena increased with water depth. Our results indicate that predation pressure, intraspecific competition, and food limitation might be responsible for variation in zebra mussel density and population size structure in space and time and that fish predation might have strong top-down effects on zebra mussel populations.
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| 27. |
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| 28. |
- Naddafi, Rahmat
(författare)
-
Predator Diversity Effects in an Exotic Freshwater Food Web
- 2013
-
Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 8
-
Tidskriftsartikel (refereegranskat)abstract
- Cascading trophic interactions are often defined as the indirect effects of a predator on primary producers through the effect of the predator on herbivores. These effects can be both direct through removal of herbivores [density-mediated indirect interactions (DMIIs)] or indirect through changes in the behavior of the herbivores [trait-mediated indirect interactions (TMIIs)]. How the relative importance of these two indirect interactions varies with predator diversity remains poorly understood. We tested the effect of predator diversity on both TMIIs and DMIIs on phytoplankton using two competitive invasive dreissenid mussel species (zebra mussel and quagga mussel) as the herbivores and combinations of one, two or all three species of the predators pumpkinseed sunfish, round goby, and rusty crayfish. Predators had either direct access to mussels and induced both TMII and DMII, or no direct access and induced only TMII through the presence of risk cues. In both sets of treatments, the predators induced a trophic cascade which resulted in more phytoplankton remaining with predators present than with only mussels present. The trophic cascade was weaker in three-predator and two-predator treatments than in one-predator treatments when predators had direct access to dreissenids (DMIIs and TMIIs). Crayfish had higher cascading effects on phytoplankton than both pumpkinseed and round goby. Increased predator diversity decreased the strength of DMIIs but had no effect on the strength of TMIIs. The strength of TMIIs was higher with zebra than quagga mussels. Our study suggests that inter-specific interference among predators in multi-species treatments weakens the consumptive cascading effects of predation on lower trophic levels whereas the importance of predator diversity on trait mediated effects depends on predator identity.
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| 29. |
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| 30. |
- Naddafi, Rahmat
(författare)
-
Predator-induced morphological defences in two invasive dreissenid mussels: implications for species replacement
- 2014
-
Ingår i: Freshwater Biology. - : Wiley. - 0046-5070 .- 1365-2427. ; 59, s. 703-713
-
Tidskriftsartikel (refereegranskat)abstract
- Induced morphological defences as a response to chemical cues from predators are common in aquatic systems. We evaluated predator-induced defences and the costs of these responses measured as growth rate reductions in two invasive mussel species.One mussel species (quagga mussel, Dreissena rostriformis bugensis) often dominates the other (zebra mussel, Dreissena polymorpha) in lakes where they co-occur. We exposed both species to cues from three important North American predators: round goby (Neogobius melanostomus), which is native in the ancestral range of the mussels, and pumpkinseed sunfish (Lepomis gibbosus) and rusty crayfish (Orconectes rusticus) that are native in North America.Both mussel species responded to risk cues by increasing shell thickness and decreasing growth rates. The response to round goby was smaller than the response to the two new predators.The strength of the induced response was negatively correlated with growth in both mussel species and both the strength of the induced defence and the decrease in growth were larger for zebra mussels than for quagga mussels. Survival was higher in zebra mussels than in quagga mussels, but there was no significant difference in survival among different risk cue treatments.The lower response and correlated faster growth of quagga mussels than zebra mussels in response to risk cues may be an additional reason for the replacement of zebra mussels by quagga mussels in North America, at least as long as native predators are not a major source of mortality. If true, we predict that both mussel species will co-occur after the exotic round goby becomes a dominant mussel predator in North America.
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| 31. |
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| 32. |
- Naddafi, Rahmat, et al.
(författare)
-
Spatial and temporal variations in stable isotope values (δ13C and δ15N) of the primary and secondary consumers along the southern coastline of the Caspian Sea
- 2021
-
Ingår i: Marine Pollution Bulletin. - : Elsevier BV. - 0025-326X .- 1879-3363. ; 164
-
Tidskriftsartikel (refereegranskat)abstract
- Spatial and temporal variations in stable isotope values of the coastal communities in the Caspian Sea remain poorly understood. We followed carbon stable isotope ratios (δ13C) and nitrogen stable isotope ratios (δ15N) of primary (gammarids) and secondary (common carp) consumers at four sites with different organic matter loadings along the southern coastline of the Caspian Sea from May to November 2019. Consumers from the site receiving higher sewage effluent and aquaculture wastes were more enriched in δ15N whereas those from the site receiving lower terrestrial-derived organic matter had enriched δ13C values. Trophic position of consumers varied among sites as a function of organic matter inputs but was independent of month. The observed temporal and spatial variations in the stable isotope values and C:N ratios of the primary and secondary consumers with regards to organic matter loadings, suggesting a possible effect of anthropogenic disturbance on the Caspian Sea ecosystem function.
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| 33. |
- Naddafi, Rahmat
(författare)
-
Speaking their language – Development of a multilingual decision-support tool for communicating invasive species risks to decision makers and stakeholders
- 2021
-
Ingår i: Environmental Modelling and Software. - : Elsevier BV. - 1364-8152 .- 1873-6726. ; 135
-
Tidskriftsartikel (refereegranskat)abstract
- Environmental changes due to non-native species introductions and translocations are a global concern. Whilst understanding the causes of bioinvasions is important, there is need for decision-support tools that facilitate effective communication of the potential risks of invasive non-native species to stakeholders. Decision-support tools have been developed mostly in English language only, which increases linguistic uncertainty associated with risk assessments undertaken by assessors not of English mother tongue and who need to communicate outcomes to local stakeholders. To reduce language-based uncertainty, the 'ecology-of-language' paradigm was applied when developing the Aquatic Species Invasiveness Screening Kit (AS-ISK), a decision-support tool that offers 32 languages in which to carry out screenings and communicate outcomes to stakeholders. Topics discussed include uncertainty related to language-specific issues encountered during the AS-ISK translation and the potential benefits of a multilingual decision-support tool for reducing linguistic uncertainty and enhancing communication between scientists, environmental managers, and policy and decision makers.
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| 34. |
- Naddafi, Rahmat
(författare)
-
Species identification of Sillaginid larvae (Perciformes: Sillaginidae) in the central creeks of Bushehr province – Persian Gulf using morphological and DNA barcoding methods
- 2016
-
Ingår i: Iranian scientific fisheries journal. - 2322-5998. ; 25, s. 1-9
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Sillaginids are one of the important fishes in coastal waters of Persian Gulf, whose larvae of different species are morphologically very similar to each other and identification of them to species level is very difficult. In this study a total of 4195 Sillaginidae larvae were collected from five inlets (Shif, Lashkari, Ramleh, Dubbeh, Farakeh) and one sampling site in the coastal area of Bushehr Province using a Bongo-net. Morphological and genetic methods were used to identity larvae of this family. The larvae were morphologically divided into two groups, depending on 34 or 38 myomers. The larvae with 34 myomeres were identified asSillagosihama. To identify larvae with 38 myomers, 12 individuals of postflexion larvae were selected and the morphological characteristic such as number of dorsal and anal fins as well as DNA barcoding of COI were used. According to morphological characteristics, the larvae were divided into two species;SillagoarabicaandSillagoattenuata. Genetic studies was done by sequencing of 625 base pair of COI gene. Genetic distances calculated using K2P model between these two species was 18% to 19.7% which indicate that DNA barcoding confirms morphological method and it can be used for identifying younger larvae whose fin rays have not been developed and are unidentifiable with morphological methods
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| 35. |
- Naddafi, Rahmat, et al.
(författare)
-
Status and perspectives for pikeperch (Sander lucioperca) stocks in the Baltic Sea region and central Europe
- 2024
-
Ingår i: Estuarine, Coastal and Shelf Science. - 0272-7714 .- 1096-0015. ; 303
-
Tidskriftsartikel (refereegranskat)abstract
- Pikeperch (Sander lucioperca) is a European fresh and brackish water piscivorous fish, important as a key predator and a valuable fisheries species. Despite concerns that some stocks are depleting due to overfishing and environmental changes, stock assessments are implemented sporadically. We provide an overview of data collection and population assessments currently used for nine pikeperch stocks across six European countries and apply a unified assessment framework (Bayesian surplus production models) to evaluate population status and trends. Our results show that three stocks, including two in the Baltic Sea, are strongly depleted, with estimated biomasses considerably lower than the biomass at maximum sustainable yield (BMSY). Other stocks are close to their estimated BMSY. Further, recent population trends suggest that only one stock (Kvädöfjärden) is increasing, whereas three (Curonian Lagoon, Lipno, Galtfjärden) are rapidly declining. In most cases the stocks with a favorable status or signs of recovery were also those for which strong management strategies have been implemented. Importantly, although most stocks are strongly targeted by recreational fishing, estimates of recreational catch are highly uncertain. We highlight an urgent need to improve pikeperch scientific monitoring and assessment of recreational catches.
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| 36. |
- Naddafi, Rahmat, 1975-, et al.
(författare)
-
Stoichiometric constraints do not limit successful invaders : zebra mussels in Swedish lakes
- 2009
-
Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 4:4, s. e5345-
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Elemental imbalances of carbon (C): nitrogen (N): phosphorus (P) ratios in food resources can constrain the growth of grazers owning to tight coupling between growth rate, RNA allocation and biomass P content in animals. Testing for stoichiometric constraints among invasive species is a novel challenge in invasion ecology to unravel how a successful invader tackles ecological barriers in novel ecosystems.Methodology/Principal Findings: We examined the C:P and N:P ratios and the condition factor of a successful invader in lakes, the zebra mussel (Dreissena polymorpha), collected from two Swedish lakes. Concurrently, we analyzed the elemental composition of the food (seston) and tissue of the mussels in which nutrient composition of food and mussels varied over time. Zebra mussel condition factor was weakly related to the their own tissue N:P and C:P ratios, although the relation with the later ratio was not significant. Smaller mussels had relatively lower tissue N:P ratio and higher condition factor. There was no difference in C:P and N:P ratios between seston and mussels' tissues. Our results indicated that the variation in nutrient stoichiometry of zebra mussels can be explained by food quality and quantity. Conclusions/Significance: Our study suggests that fitness of invasive zebra mussels is not constrained by nutrient stoichiometry which is likely to be important for their proliferation in novel ecosystems. The lack of imbalance in C:P and N:P ratios between seston and mussels along with high tissue C:P ratio of the mussel allow them to tolerate potential P limitation and maintain high growth rate. Moreover, zebra mussels are able to change their tissue C:P and N:P ratios in response to the variation in elemental composition of their food. This can also help them to bypass potential nutrient stoichiometric constraints. Our finding is an important step towards understanding the mechanisms contributing to the success of exotic species from stoichiometric principles.
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| 37. |
- Naddafi, Rahmat
(författare)
-
Stomach contents and stable isotopes analysis indicate Hemimysis anomala in Lake Ontario are broadly omnivorous
- 2018
-
Ingår i: Journal of Great Lakes Research. - : Elsevier BV. - 0380-1330. ; 44, s. 467-475
-
Tidskriftsartikel (refereegranskat)abstract
- Hemimysis anomala is a recent invader to North American aquatic ecosystems and is spreading rapidly throughout the Great Lakes region. This is the first littoral mysid in the North American Great Lakes; and, as such, the ecosystem effects are unknown and could be substantial. These effects depend on the role of Hemimysis in the food web and, therefore, on its diet. We examined the stomach contents of two life stages of Hemimysis from two sites in Lake Ontario during the growing season (May-November 2010). We also report the relationship between zooplankton hard parts and size for a number of potential prey species to allow the back-calculation of prey lengths from stomach contents. Both juvenile (2-5 mm) and adult Hemimysis (5-11 mm) were omnivorous, consuming phytoplankton, zooplankton, and benthos when available. However, adults appeared slightly more carnivorous and incorporated larger prey in their diets. Hemimysis were able to consume zooplankton prey up to 30% of their own length, including Bythotrephes longimanus and Cercopagis pengoi. Daphnia and Bosmina were selected over other prey by both juvenile and adult Hemimysis and were most common in stomachs during July and September when their abundances in the zooplankton were highest. Measurements of delta C-13 and delta N-15 corroborated stomach content materials, indicating an omnivorous diet which included benthic and pelagic sources. Omnivory by Hemimysis is typical of mysids in general and makes them less sensitive to seasonal dynamics of preferred prey items. (C) 2018 International Association for Great Lakes Research. Published by Elsevier B.V. All rights reserved.
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| 38. |
- Naddafi, Rahmat, et al.
(författare)
-
Sweden
- 2017
-
Ingår i: ICES WGITMO report 2017: interim report of the working group on introductions and transfers of marine organisms (WGITMO)), 13–15 March 2017, Woods Hole, USA. ICES CM 2017/SSGEPI:09. ; , s. 105-106
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 39. |
- Naddafi, Rahmat, et al.
(författare)
-
Sweden
- 2018
-
Ingår i: ICES. 2018. Interim Report of the Working Group on Introductions and Transfers of Marine Organisms (WGITMO) , 7–9 March 2018, Madeira, Portugal . ICES CM 2018/HAPISG:11. ; , s. 125 - 132
-
Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- There has been no report showing new species in Sweden since January 2017. The round goby Neogobius melanostomusis continuing to expand its range in the Baltic Sea. Pink salmon Oncorhynchus gorbuschhave been abundant in catches at the Swedish west coast in 2017. Pacific oyster Magallana gigas is expanding its distribution southwards. Two new observations of American lobsters Homarus americanus were made in the Skagerrak in 2017. Alien crabs including the Japanese shore crab Hemigrapsus sanguineus and the brush-clawed shore H. takanoi have been frequently reported in Swedish waters during 2017. Other crab spices such as the North American mud crab Rhithropanopeus harrisii and the Chinese mitten crab Eriocheir sinensiswere also observed in Sweden.
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| 40. |
- Naddafi, Rahmat, et al.
(författare)
-
The effect of seasonal variation in selective feeding by zebra mussels (Dreissena polymorpha) on phytoplankton community composition
- 2007
-
Ingår i: Freshwater Biology. - : Wiley. - 0046-5070 .- 1365-2427. ; 52:5, s. 823-842
-
Tidskriftsartikel (refereegranskat)abstract
- To investigate the impact of zebra mussels (Dreissena polymorpha) on phytoplankton community composition, temporal variability in selective feeding by the mussels was determined from April to November 2005 in a natural lake using Delayed Fluorescence (DF) excitation spectroscopy. Selective grazing by zebra mussels varied in relation to seasonal phytoplankton dynamics; mussels showed a consistent preference for cryptophytes and avoidance of chlorophytes and cyanobacteria. Diatoms, chrysophytes and dinoflagellates responded differentially to zebra mussel grazing depending on their size. Analysis of excreted products of the zebra mussels revealed that in addition to chlorophytes and cyanobacteria, phytoplankton >50 μm and very small phytoplankton (≤7 μm) were largely expelled in pseudofaeces. The zebra mussel is a selective filter-feeder that alters its feeding behaviour in relation to phytoplankton composition to capture and ingest high quality phytoplankton, especially when phytoplankton occur in preferred size ranges. Flexibility of zebra mussel feeding behaviour and variation in susceptibility among phytoplankton groups to mussel ingestion indicate that invading zebra mussels could alter phytoplankton community composition of lakes and have important ecosystem consequences.
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| 41. |
- Naddafi, Rahmat
(författare)
-
The fate of nitrogen in the Zarin-Gol River receiving trout farm effluent
- 2023
-
Ingår i: Scientific Reports. - 2045-2322. ; 13
-
Tidskriftsartikel (refereegranskat)abstract
- This study investigated the Zarrin-Gol River ecosystem in Iran to trace organic matter in the food web and evaluate the impact of aquaculture farm effluent using stable isotopes of nitrogen (delta 15N) and carbon (delta 13C). Using a previously-developed model (Islam 2005), we estimated that a trout farm in the vicinity released 1.4 tons of nitrogen into the river. This was comparable to an estimated total nutrient load of 2.1 tons of nitrogen for the six-month fish-rearing period based on a web-based constituent load estimator (LOADEST). A model estimate of river nitrogen concentration at the time of minimum river discharge (100 L/s) was 2.74 mg/L. Despite relatively high nitrogen loading from the farm, isotope data showed typical food web structure. Several biological groups had elevated delta 13C or delta 15N values, but there was limited evidence for the entry of organic matter from the trout farm into the food web, with sites above and below trout farms having inconsistent patterns in 15N enrichment. By coupling nitrogen load modeling with stable isotope analysis we showed that stable isotopes might not be effective tracers of organic matter into food webs, depending on surrounding land use and other point sources of nutrients. The Zarrin-Gol River ecosystem, like other basins with high human population density, remains vulnerable to eutrophication in part due to trout farm effluent.
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| 42. |
- Naddafi, Rahmat, 1975-
(författare)
-
The Invasion of the Zebra Mussel - Effects on Phytoplankton Community Structure and Ecosystem Function
- 2007
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Biological invasion has become a major threat to economy, ecology, global biodiversity and ecosystem function of aquatic ecosystems. The main aim of the thesis was to study the effects of the zebra mussel (Dreissena polymorpha), a versatile invasive species, on phytoplankton dynamics and ecosystem function of lakes.In a first attempt, I compared the density of Dreissena and the physicochemical data of ecosystems that it invaded among North American and European lakes to identify important factors in its invasion success. Secondly, I investigated the impact of zebra mussels on phytoplankton community composition in a natural lake. Thirdly, I evaluated whether zebra mussel feeding behavior were affected by the presence of predatory waterborne cues. Finally, I examined the effect of Dreissena on seston stoichiometry.A Generalized Additive Model revealed that a joint effect of surface area, mean depth, total phosphorus and calcium concentrations can explain the variability in Dreissena density. Selective grazing by zebra mussels varied in relation to seasonal phytoplankton dynamics. Risk cues released by predators affected both feeding rate and prey selection of the mussels and had cascading indirect effects on phytoplankton biomass and community structure. I found that the flux in nutrients caused by differences in zebra mussel consumption lead to a variation in phytoplankton nutrient limitation.The flexibility of zebra mussel feeding behavior and variation in susceptibility among phytoplankton groups to mussel ingestion indicate that invading zebra mussels could alter phytoplankton community composition of lakes and have important ecosystem consequences. The results of this thesis contribute to the growing evidence that predators indirectly affect resource dynamics and food web structure through their non-lethal effects on consumers. The results suggested that zebra mussel can indirectly both reduce and increase the energy transfer efficiency from primary producers to upper trophic levels in the pelagic and benthic food webs, respectively.
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| 43. |
- Naddafi, Rahmat, et al.
(författare)
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Variation in tissue stoichiometry and condition index of zebra mussels in invaded Swedish lakes
- 2012
-
Ingår i: Biological Invasions. - : Springer Science and Business Media LLC. - 1387-3547 .- 1573-1464. ; 14:10, s. 2117-2131
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Tidskriftsartikel (refereegranskat)abstract
- We examined the spatial variation in carbon:nitrogen:phosphorus (C:N:P) stoichiometry and condition index of the zebra mussel (Dreissena polymorpha), non-indigenous species, in four Swedish lakes with different productivity. Within-lake variability was observed in tissue C:N molar ratios of Dreissena in all lakes and in tissue C:P ratio only in three lakes. Depth had no effect on tissue C:P and N:P ratios of Dreissena. A positive correlation was found between C:N:P stoichiometry of seston and elemental composition of zebra mussel in one of the lakes. Tissue C:N and N:P ratios were the main factors that related to zebra mussel condition index. Zebra mussel condition was positively related to tissue C:N ratio. Smaller Dreissena had higher C:N ratio than larger Dreissena in two of the four lakes. Zebra mussels in the lake with highest productivity had lower C:P and N:P ratios than zebra mussels in the lake with lowest productivity. Our study suggests that the zebra mussel may modify their phosphorus content in relation to lake trophic state, and therefore cope with stoichiometric constraints which may explain the invasion success of this and other related species.
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- Olsson, Jens, et al.
(författare)
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A pan-Baltic assessment of temporal trends in coastal pike populations
- 2023
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Ingår i: Fisheries Research. - : Elsevier BV. - 0165-7836 .- 1872-6763. ; 260
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Tidskriftsartikel (refereegranskat)abstract
- The northern pike (Esox lucius) is an iconic predatory fish species of significant recreational value and ecological role in the Baltic Sea. Some earlier studies indicate local declines of pike in the region, but a thorough spatial evaluation of regional population trends of pike in the Baltic Sea is lacking. In this study, we collate data from 59 unique time-series from fisheries landings and fishery-independent monitoring programs to address temporal trends in pike populations since the mid-2000 ' s in eight countries surrounding the Baltic Sea. In a common analysis considering all time-series in concert, we found indications of an overall regional temporal decline of pike in the Baltic Sea, but trends differed among countries. Individual negative trends in time-series were moreover found in several regions of the Baltic Sea, but predominantly so in the central and southern parts, while positive trends were only found in Estonia and northern Finland. The mix of data used in this study is inherently noisy and to some extent of uncertain quality, but as a result of the overall negative trends, together with the socioeconomic and ecological importance of pike in coastal areas of the Baltic Sea, we suggest that actions should be taken to protect and restore pike populations. Management measures should be performed in combination with improved fishery-independent monitoring programs to provide data of better quality and development of citizen-science approaches as a data source for population estimates. Possible measures that could strengthen pike populations include harvest regulations (including size limits, no-take areas and spawning closures), habitat protection and restoration, and an ecosystem-based approach to management considering also the impact of natural predators.
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| 48. |
- Olsson, Jens, et al.
(författare)
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Abundance of coastal fish key functional groups. HELCOM core indicator report
- 2017
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This core indicator evaluates the abundance of selected functional groups of coastal fish in the Baltic Sea. As a rule, good status is achieved when the abundance of piscivores (i.e. fish that feed on other fish) is above a site-specific threshold value, and the abundance of cyprinids or mesopredators (i.e. midtrophic-level fish) is within an acceptable range for the specific site. The status of functional groups of coastal fish in the Baltic Sea has been evaluated by assessing the status of piscivores and cyprinids/mesopredators during the period 2011-2015. For piscivores, good status is achieved in 24 out of a total of 29 monitoring locations, and for 13 coastal HELCOM assessment units out of the 16 that were evaluated. For cyprinids/mesopredators, good status is only achieved in 15 of the 27 monitored locations and thus in seven of the 16 evaluated assessment units. In the locations classified as not good, the abundance of cyprinids was too high in all but one (Hiiumaa, Estonia) of the 12 locations. The environmental status indicated by piscivores is hence slightly better compared to that indicated by cyprinids. Generally, the status of piscivores is better in more northern areas compared to more central areas. For cyprinids/mesopredators, good status is not achieved in the Swedish part of the Quark and Åland Sea, in all Finnish coastal waters except for the Bothnian Bay, and in Estonian and Latvian coastal waters. The level of confidence of the assessment differs across areas and regions as a result of differences in monitoring methodology as well as in some countries poor temporal and spatial coverage of monitoring due to poor financial support for monitoring. The methodological confidence is high in all areas and the confidence in the accuracy of the assessment is high in majority of the assessment units. The confidence in the temporal coverage is high in all areas except for the Latvian and Lithuanian areas, and the confidence in spatial representa bility is the highest in the Finnish areas but poorer in other countries. The indicator is operational in the coastal waters of most countries bordering the Baltic Sea. For the time being, it is not applicable in some areas where coastal fish monitoring data are scarce and further studies as well as time series are needed to yield a reliable as sessment of these areas. In the future, in line with increasing knowledge, the indicator might undergo further development
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