Two fisheries scientific papers published Towards better fisheries management in Seychelles By Vidya Gappy |27 February 2021
The Seychelles Fishing Authority (SFA) yesterday presented the results of two scientific research papers that have recently been published to enable better management of fisheries in Seychelles.
Both papers have been spearheaded by SFA in collaboration with various partners.
Fisheries scientists Nathalie Bodin from the non-governmental organisation ‘Sustainable Ocean Seychelles’and Rodney Govinden, manager of research at SFA, are the two main authors of one scientific paper entitled ‘Morphometrics of 39 fishes from the Seychelles artisanal fisheries’. The paper highlights important discoveries made on the length and weight relationship of 39 marine species from 10 families caught in the Seychelles waters by the artisanal fishery and sampled from 2009 to 2020.
These types of scientific research is highly important as it will support the application of accurate size-based analyses for Seychelles fisheries survey data, and therefore enables a better understanding of the ecology of the reef-associated fish component of marine ecosystems and food webs, and improve fisheries research management.
These researches have been funded partly by SFA and European Union funds.
According to Mr Govinden, “a total of 5478 fishes were sampled between 2009 and 2020 to assess length–weight, length–length and weight–weight relationships in 39 marine species from 10 families caught in the Seychelles waters by the artisanal fishery. Two types of length (total length TL, fork length FL) and three types of weight (whole weight WT, gutted weight GW and gilled-gutted weight GGW) were measured. The parameters of the relationships were estimated using the log transformed allometric model with bias correction. Our results include length–weight, length–length and weight–weight relationships for 39, 20 and 18 species, respectively. Our length–weight data and resulting relationships were compared against FishBase database for 36 species and were in the Bayesian 95% confidence interval of the relationships available for 33 species and above for Gnathanodonspeciosus, Lutjanusgibbus and Variolalouti. Finally, for five abundant and widely dispersed species we tested for spatial differences in morphometric relationships between the Mahé Plateau and three southern atoll groups. Significant differences were found for two species only, but their magnitude was small. We thus argued for the regression relationships based on pooled data to be used for most types of population and community analyses. The availability of these morphometric relationships will support the application of accurate size-based analyses for Seychelles fisheries survey data, and so enhance understanding of the ecology of the reef-associated fish component of marine ecosystems and food webs, and improve fisheries research management.”
Ms Dodin added that this type of research work is important for SFA as they are the ones monitoring the amount of fish in the Seychelles seas and also make decisions about stock assessment.
‘Diet of spiny lobsters from Mahé Island reefs, Seychelles inferred by trophic tracers’
A second research was also published recently entitled ‘Diet of spiny lobsters from Mahé Island reefs, Seychelles inferred by trophic tracers’. Rodney Govinden is also one of the main authors of this paper.
The paper notes that “Spiny lobsters (Panuliruslongipes, P. penicillatus and P. versicolor) are an important resource in Seychelles, where they inhabit coastal carbonate and granite reefs that have been impacted by multiple coral bleaching events over the past two decades. Little is known about their biology and ecology in this region. Interspecific competition for food resources was previously suggested, but no quantitative data on the diet of spiny lobsters were available. Using carbon and nitrogen stable isotope compositions and fatty acid profiles of three spiny lobster species and their potential prey, a Bayesian mixing model for diet estimation was applied to compare the diet proportions of spiny lobsters among species and between reef types (carbonate and granite reefs). Model outputs suggested the three lobster species consume mainly crustaceans (Anomoura hermit crabs; half of the diet), then Echinoidea (sea urchins), algae and molluscs. P. versicolor was found to consume slightly more molluscs and algae than the two other studied species, which was consistent with its lower trophic level (2.4 vs 2.8 for the two other species). Trophic level did not increase with carapace length of spiny lobsters, but large individuals had higher carbon isotopic values suggesting that they might feed closer to the coast or more on detritus feeders than their smaller congeners. Diets of spiny lobsters were fairly similar between carbonate and granite reefs, except that lobster inhabiting granite reefs consumed more sea urchins. While our overall findings were consistent with gut contents of Panulirus spp. from other world regions, they should be confirmed, as the discrimination of several prey based on trophic tracers was low, which increased mixing model uncertainty”.
SFA in collaboration with other institutions will keep doing researches in our waters in order to make sure we practice safe and sound fishing.