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Stepwise function of natural growth for Scylla serrata in East Africa: a valuable tool for assessing growth of mud crabs in aquaculture 下载免费PDF全文
Per‐Olav Moksnes David Oersted Mirera Emma Björkvik Muumin Iddi Hamad Humphrey Matalu Mahudi Daniel Nyqvist Narriman Jiddawi Max Troell 《Aquaculture Research》2015,46(12):2938-2953
Predicting growth is critical in aquaculture, but models of growth are largely missing for mud crab species. Here, we present the first model of natural growth in juvenile and adult mud crabs Scylla serrata from East Africa using a stepwise growth function based on data on intermoult periods and growth at moult from field mark‐recapture, pond and laboratory studies. The results showed a sigmoid growth pattern in carapace width and suggest that S. serrata in East Africa will reach 300 g and sexual maturity ~9.9 months after settlement, and a commercial size of 500 g after 12.4 months. Analyses of the literature identified several issues with the common praxis to compare standard growth measures between aquaculture studies with different initial size or growing periods. Using the new growth function to estimate the proportional difference between modelled and obtained growth as an alternative method, we show that growth rates of S. serrata cultured in cage systems, which are dominant in East Africa, was <40% of the estimated natural growth and growth obtained in pond systems. The analysis also indicated that growth rates of S. serrata in Southeast Asia was over 50% higher compared with similar culture systems in East Africa, and that different species of mud crabs had large differences in growth rates. This study shows that growth in the present mud crab aquaculture systems in East Africa is below their expected potential. Further work is needed to identify the factors behind this observation. 相似文献
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Blandina R Lugendo Ivan Nagelkerken Narriman Jiddawi Yunus D Mgaya Gerard Van Der Velde 《Fisheries Science》2007,73(6):1213-1223
ABSTRACT: By using a seine net, fish samples were taken from the nonestuarine Chwaka Bay (Zanzibar, Tanzania) from the mangroves, mud/sand flats and seagrass beds. Sampling was done twice per month between November 2001 and October 2002. In total, 150 fish species belonging to 55 families were identified. Diversity ( H' ) ranged from 1.9 in mud/sand flats to 3.4 within the Chwaka seagrass beds. Mean density of fishes was significantly higher in the mangrove creeks than in any other habitat (mean = 238.7 ind./1000 m2 ). Highest, but non-significantly different mean biomasses were recorded in the mangrove creeks (1.7 kg/1000 m2 ) and in the Marumbi seagrass beds (1.6 kg/1000 m2 ). The mangrove channel had the lowest biomass (0.6 kg/1000 m2 ). A high overlap in species composition (as high as 93.4% similarity) was found for adjoining habitats (i.e. mangrove creeks and mangrove channel), while habitats that were far apart showed low overlap (6.6% similarity for the Marumbi seagrass beds and mangrove creeks). On average, 58.4 and 63.2% in terms of abundance and biomass, respectively, of the fish assemblage of Chwaka Bay were of commercial fishery importance. Thus, Chwaka Bay appears to be an important juvenile habitat for various commercially important fish species. 相似文献
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Elizabeth H. M. Tyler Andrea manica Narriman Jiddawi Martin R. Speight 《水产资源保护:海洋与淡水生态系统》2011,21(3):231-238
- 1. Completely banning fishing from coral reefs is now accepted to have significant benefits for marine biodiversity and in many cases, fisheries. However, the benefits of regulating fishing on coral reefs, by restricting the methods used, or the total amount of fishing, are less well understood, even though such regulations are much more likely to be supported by fishermen.
- 2. This study assesses whether banning illegal, destructive fishing methods and reducing the numbers of fishermen visiting from outside an area benefits a coral reef fishery, despite unregulated fishing by local fishermen using non‐destructive methods.
- 3. The abundance, biomass, mean length, and species richness of nine commercially important fish families are compared across ten independent patch reefs inside and outside the 470 km2 Menai Bay Conservation Area in Zanzibar, Tanzania.
- 4. Even after taking into account the effect of differences in habitat and the distance between reefs, 61% (±19.7%) more fish species were found in regulated than unregulated reefs. Fish abundance, biomass, and length were not affected, suggesting that banning destructive fishing may improve biodiversity, but that further regulations may be required to improve fish stocks.Copyright © 2011 John Wiley & Sons, Ltd.
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