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- Tano, Stina, 1983-
(författare)
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Seaweed in the tropical seascape : Importance, problems and potential
- 2016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The increasing demand for seaweed extracts has led to the introduction of non-native seaweeds for farming purposes in many tropical regions. Such intentional introductions can lead to spread of non-native seaweeds from farming areas, which can become established in and alter the dynamics of the recipient ecosystems. While tropical seaweeds are of great interest for aquaculture, and have received much attention as pests in the coral reef literature, little is known about the problems and potential of natural populations, or the role of natural seaweed beds in the tropical seascape.This thesis aims to investigate the spread of non-native genetic strains of the tropical macroalga Eucheuma denticulatum, which have been intentionally introduced for seaweed farming purposes in East Africa, and to evaluate the state of the genetically distinct but morphologically similar native populations. Additionally it aims to investigate the ecological role of seaweed beds in terms of the habitat utilization by fish and mobile invertebrate epifauna. The thesis also aims to evaluate the potential of native populations of eucheumoid seaweeds in regard to seaweed farming.The initial results showed that non-native E. denticulatum is the dominating form of wild eucheumoid, not only in areas in close proximity to seaweed farms, but also in areas where farming has never occurred, while native eucheumoids are now scarce (Paper I). The low frequency of native E. denticulatum in seaweed beds, coupled with a low occurrence of reproductive structures, indicates that the effective population size may be low, which in turn may be a threat under changing environmental conditions. These results, combined with indications that seaweeds may be declining in East Africa, illustrates the need for attaining a better understanding of the ecological role of tropical seaweed habitats. The studies on the faunal communities of seaweed beds showed that they are species rich habitats, with high abundances of juvenile fish and mobile epifauna (Paper II and III), strongly indicating that these habitats should be considered for future seascape studies and management actions. Productivity in East African seaweed farming is decreasing, and as the current cultivation is based on a single non-indigenous haplotype, a more diverse genetic base has been suggested as a means to achieve a more productive and sustainable seaweed farming. Although our results show that East African E. denticulatum has a lower growth rate than the currently used cultivar (Paper IV), the several native haplotypes that are present in wild populations illustrates that, though a demanding endeavour, there is potential for strain selection within native populations.
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| 2. |
- Wilson, Shaun K., et al.
(författare)
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The contribution of macroalgae-associated fishes to small-scale tropical reef fisheries
- 2022
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Ingår i: Fish and Fisheries. - : Wiley. - 1467-2960 .- 1467-2979. ; 23:4, s. 847-861
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Tidskriftsartikel (refereegranskat)abstract
- Macroalgae-dominated reefs are a prominent habitat in tropical seascapes that support a diversity of fishes, including fishery target species. To what extent, then, do macroalgal habitats contribute to small-scale tropical reef fisheries? To address this question we: (1) Quantified the macroalgae-associated fish component in catches from 133 small-scale fisheries, (2) Compared life-history traits relevant to fishing (e.g. growth, longevity) in macroalgal and coral-associated fishes, (3) Examined how macroalgae-associated species can influence catch diversity, trophic level and vulnerability and (4) Explored how tropical fisheries change with the expansion of macroalgal habitats using a case study of fishery-independent data for Seychelles. Fish that utilised macroalgal habitats comprise 24% of the catch, but very few fished species relied entirely on macroalgal or coral habitats post-settlement. Macroalgal and coral-associated fishes had similar life-history traits, although vulnerability to fishing declined with increasing contribution of macroalgae association to the catch, whilst mean trophic level and diversity peaked when macroalgal-associated fish accounted for 20%–30% of catches. The Seychelles case study revealed similar total fish biomass on macroalgal and coral reefs, although the biomass of primary target species increased as macroalgae cover expanded. Our findings reinforce that multiple habitat types are needed to support tropical fishery stability and sustainability. Whilst coral habitats have been the focus of tropical fisheries management, we show the potential for macroalgae-associated fish to support catch size and diversity in ways that reduce vulnerability to overfishing. This is pertinent to seascapes where repeated disturbances are facilitating the replacement of coral reef with macroalgal habitats.
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