| 1. |
- Both, Adrianus, 1985-, et al.
(författare)
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Lipid composition of Mytilus edulis reared on organic waste from a Gadus morhua aquaculture facility
- 2011
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Ingår i: Aquatic Living Resources. - : EDP Sciences. - 0990-7440 .- 1765-2952. ; 24:3, s. 295-301
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to determine biochemical changes occurring in blue mussels (Mytilus edulis) fed effluent from an Atlantic cod (Gadus morhua) aquaculture facility over a period of ten weeks, compared to those in mussels fed a commercial shellfish diet and those supplied only filtered seawater. The total lipid and fatty acid content (mg g -1 wet weight) significantly decreased for mussels fed effluent during the experiment. The only change in the lipid class composition (% total lipid) at the end of the experiment was a significant increase in the proportion of acetone mobile polar lipids. There were several significant changes in the fatty acid composition (% total fatty acid) including an increase in the proportion of 18:1ω9, 18:2ω6, 20:4ω6, 21:5ω3 and the dienoic non-methylene-interrupted fatty acids 20:2a and 22:2b and significant decreases in the proportions of 16:0, 18:4ω3 and 20:5ω3. The increase in non-methylene interrupted dienes suggests that the amount of essential fatty acids in the effluent may be insufficient for optimal mussel growth. The presence of the terrestrial plant marker 18:2ω6 in both the fish feed and the effluent and its increased proportion in mussels fed effluent suggest that this fatty acid may have potential as a marker for aquaculture wastes.
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| 2. |
- Delmas, D, et al.
(författare)
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Exoproteolytic activity determined by flow injection analysis: potential importance for bacterial growth in coastal marine ponds
- 1994
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Ingår i: Aquatic Living Resources. - : EDP Sciences. - 0990-7440 .- 1765-2952. ; 7:1, s. 17-24
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Tidskriftsartikel (refereegranskat)abstract
- The measurement of the fluorescent 4-methyl-7-coumarinylamine released from the hydrolysis of a non-fluorescent peptide model substrate by exoproteolytic enzymes has been adapted to flow injection analysis (FIA). FIA allows samples to be processed very quickly (less than 2 min. for triplicate determinations) with good sensitivity (< 0.1 muM) and reproducibility (relative standard deviation < 3 % at the 0.2 muM level). In a coastal marine pond, exoproteolytic activity was closely related to bacterioplankton biomass. The high activity measured in pond water (maximum velocity: V(M) almost-equal-to 1.46 to 2.54 muM.h-1) emphasizes the importance of dissolved protein hydrolysis for bacterial growth and for dissolved organic nitrogen cycling. The mean turnover time of dissolved peptides was 7.6 days, and amino acids liberated by exoproteolytic activity could potentially support, on average, 40 % of the bacterial nitrogen demand.
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| 3. |
- Eklöf, Johan S., et al.
(författare)
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How do seaweed farms influence fishery catches in a seagrass-dominated setting in Chwaka Bay, Zanzibar?
- 2006
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Ingår i: Aquatic Living Resources. - : EDP Sciences. - 0990-7440 .- 1765-2952. ; 19:2, s. 137-147
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Tidskriftsartikel (refereegranskat)abstract
- Seaweed farming is often depicted as a sustainable form of aquaculture, contributing to poverty reduction and financial revenues in producer countries. However, farms may negatively affect seagrasses and associated organisms (e.g. invertebrate macrofauna) with possible effects on the flow of ecosystem goods and services to coastal societies. The present study investigates the influence of a seaweed farm, and the farmed seaweed Eucheuma denticulatum in particular, on fishery catches using a traditional fishing method ("madema" basket traps) in Chwaka bay (Zanzibar, Tanzania). The results suggest that a seaweed farm, compared to a seagrass bed, had no influence on catch per unit effort (no. of individuals per catch, or catch weight) or no. of species per catch, but significantly affected catch composition (i.e. how much that was caught of which species). The two species contributing most to differences between the sites were two economically important species; the herbivorous seagrass rabbit fish Siganus sutor, which was more common in the seaweed site and is known to graze on the farmed algae; and the benthic invertebrate feeder chloral wrasse Cheilinus chlorourus, more common in the seagrass site. Compared to vegetation-free bottoms, however, the catches were 3-7 times higher, and consisted of a different set of species (ANOSIM global R > 0.4). As traps placed close to the seaweeds fished three times more fish than traps placed on sand patches within the seaweed farm, the overall pattern is attributed to the presence of submerged vegetation, whether seagrass or seaweed, probably as shelter and/or food for fish. However, qualitative differences in terms of spatial and temporal dynamics between seagrass beds with and without seaweed farms, in combination with other factors such as institutional arrangements, indicate that seaweed farms cannot substitute seagrass beds as fishing grounds.
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| 4. |
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| 5. |
- Eriksson, Hampus, 1979-, et al.
(författare)
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Resource degradation of the sea cucumber fishery in Zanzibar, Tanzania : a need for management reform
- 2010
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Ingår i: Aquatic Living Resources. - : EDP Sciences. - 0990-7440 .- 1765-2952. ; 23, s. 387-398
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Tidskriftsartikel (refereegranskat)abstract
- This study assessed the Zanzibar sea cucumber fishery using a multidisciplinary approach. Data was collected by (i) interviewing various groups of actors in the fishery and reviewing management documentation and legislation, (ii) by monitoring catches and (iii) through a visual census of coastal sea cucumber populations in areas open and closed to fishing. The fishery showed clear signs of being unsustainable with high fishing effort, and weak formal and informal management institutions. The fishery operation was characterised by an intricate cross-scale structure with both fishers and sea cucumber products being transported across national borders. The visual census of commercial sea cucumber stocks at three sites open to fishing around Zanzibar showed low densities across the range of sea cucumber value groups including low value species. Furthermore, the diversity of commercial sea cucumber species was lower in fished reefs than on a protected reef. The poor status of the sea cucumber populations was confirmed by the perception of an overfished resource by the interviewed actors active in the fishery. This was also depicted by the paucity of high value species, and high representation of low value and newly commercialised species in fishers catch. We conclude that the current state of Zanzibar’s sea cucumber populations is compromising the fisheries self-replenishment and existence and that the fishery is in urgent need of a complete management reform.
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| 6. |
- Morvezen, R., et al.
(författare)
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Multiplex PCR sets of novel microsatellite loci for the great scallop Pecten maximus and their application in parentage assignment
- 2013
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Ingår i: Aquatic Living Resources. - : EDP Sciences. - 0990-7440 .- 1765-2952. ; 26:3, s. 207-213
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Tidskriftsartikel (refereegranskat)abstract
- We report the isolation, development and multiplex optimisation of 12 new microsatellite loci for the great scallop, Pecten maximus. Diversity was moderate to high, with number of alleles ranging from 4 to 20 and observed heterozygosity between 0.28 and 0.88. Progeny produced in a commercial hatchery was used to test locus power for parentage assignment. The percentage of offspring that was unambiguously assigned to a unique pair of parents was 97% (software package CERVUS-COLONY). Parentage assignment revealed that 22% of the studied progeny resulted from unplanned crosses. Effective population size of the study progeny was also estimated. Our study illustrates the power of microsatellites for the genetic monitoring of hatchery-produced great scallops.
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| 7. |
- Nordlund, Lina, 1979-, et al.
(författare)
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Changes in an East African social-ecological seagrass system : invertebrate harvesting affecting species composition and local livelihood
- 2010
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Ingår i: Aquatic Living Resources. - : EDP Sciences. - 0990-7440 .- 1765-2952. ; 23:4, s. 399-416
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Tidskriftsartikel (refereegranskat)abstract
- Seagrass meadows support high biodiversity and are important for invertebrate harvesting activities in developing countries. The aim of this study was to estimate the social and ecological effects of invertebrate harvesting, i.e. how this exploitation may affect/has affected seagrass variables (biomass, shoot density and canopy height), macrofaunal community structure, the use and importance of these resources for the livelihood of local people over time. A multi-disciplinary approach was used, including interviews with harvesters, observations of the number/activities of invertebrate harvesters, and a biological field study in Zanzibar, Tanzania. The study showed that women/children harvest invertebrates, and they prefer large seagrass patches, high to medium shoot density, and high seagrass cover. All interviewees said they had noticed a decline in seagrass distribution over the last decade, >20% considered it a large decline. Interviewees also reported decreased numbers of animals, but no change in the number of animal species over the last decade. The main reasons for the decline of seagrass and animals according to interviewees, are an increase in the number of harvesters, and a change in attitude, i.e. people being less careful about the intertidal zone and seagrasses. Invertebrate harvesting was found important for food security and provision of cash income. The current average catch weight was ca. 2 kg/collection day/person, and 3 kg and 5 kg, 5–10 and 30 years ago respectively according to interviewees. At present, the harvesting women earn ca 60–70% and ca 40% of what they would have if catches were the same sizes as they were 5–10 and 30 years ago respectively, according to our calculations. The field sampling within seagrass beds showed that an inaccessible/remote site had significantly higher invertebrate abundance and species richness/diversity than an exploited site (ANOVA). Multivariate statistics further revealed weak but significant differences for animal abundance and biomass between these sites. By combining findings from both interviews and field sampling this study shows that invertebrate harvesters can influence macrofaunal community structure in seagrass meadows, which in turn results in negative impacts on local harvesters’ economy and livelihood.
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| 8. |
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| 9. |
- Vitale, Francesca, et al.
(författare)
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Growth and maturity of sprat (Sprattus sprattus) in the Kattegat and Skagerrak, eastern North Sea
- 2015
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Ingår i: Aquatic Living Resources. - : EDP Sciences. - 0990-7440 .- 1765-2952. ; 28, s. 127-137
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Tidskriftsartikel (refereegranskat)abstract
- Information on fish biology, as growth and reproduction, is an essential first step for a sound assessment and management of a fishery resource. Here we analyzed the annual cycle of body condition factor (K), gonadosomatic index (GSI) and maturity of sprat from the Skagerrak and Kattegat as well as from the Skagerrak inner fjords (Uddevalla fjords). The results show an inverse yearly pattern for K and GSI in both areas, K being the highest in autumn and lowest in spring, while the GSI index was highest in spring and lowest in autumn. The annual highest proportion of spawning fish was recorded from May to July, indicating the late spring and early summer as the main spawning period for sprat in these areas. Male sprat reached maturity at a higher size in the Uddevalla fjords compared to Skagerrak and Kattegat, while negligible differences were shown by females. The K, GSI and size-at-age were the lowest in the Uddevalla fjords, while K and GSI were the highest in the Skagerrak, potentially related to the different environmental conditions encountered in the different areas. All in all the present results furnish important information about the biology of the sprat in the area that is highly relevant in stock assessment and management. The potentiality for the sprat inhabiting the Uddevalla fjords to be a different sub-population should be addressed through further investigations.
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| 10. |
- Waldo, Staffan
(författare)
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Impact of a simultaneous reduction in fishing subsidies and introduction of efficient management of rents: the case of the Northwest Spanish fleet
- 2018
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Ingår i: Aquatic Living Resources. - : EDP Sciences. - 0990-7440 .- 1765-2952. ; 31
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Tidskriftsartikel (refereegranskat)abstract
- Subsidies to the fishing sector have long been criticized for fueling over-fishing, and a reduction in subsidies is currently on the agenda in the negotiations within theWorld Trade Organization (WTO). This article analyzes the role of subsidies and other management measures for Spain, one of the largest fishing nations within the EU. A static bio-economic model is used to analyze the effect of simultaneous elimination of subsidies and introduction of an economically efficient management system for the Northwest Spanish fleet. It is concluded that improvements in management would bring substantial rents to the industry, up to (sic) 164 million, irrespective of subsidy level, but also a reduction in fishing effort of almost 60%. Under a management scheme that maximizes economic rents, elimination of subsidies in the fishery would increase social welfare, induced by a decrease in the equilibrium fishing effort level. However, the impact of subsidies under this scheme is limited.
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