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Gear selectivity of fishery target resources in Lake Koka, Ethiopia: evaluation and management implications

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Abstract

We evaluated the statistical models that best describe the selectivity of common fishing gears used in Lake Koka for four freshwater species widely distributed in Ethiopia and elsewhere: tilapia Oreochromis niloticus (L.), catfish Clarias gariepinus (B.), common carp Cyprinus carpio (L.), and barb Labeobarbus intermedius (R.). Sampling was conducted from October 2012 to March 2013 using gillnets (60, 80, 100, and 120 mm stretched mesh), longlines (4/0, 6/0, and 8/0 hooks size), and a beach seine with covered codend. Size at maturity (L m) was determined for each species. The SELECT method was used to explore unimodal selectivity models for gillnet and longline gears, while the logistic function was used for beach seine. Results show that a log-normal model best described gillnet selectivity for all species, while a normal scale model best described longline selectivity for C. gariepinus. Gillnets with ≥100 mm mesh and longlines with >4/0 hooks could be safely used, as they allow target resources to attain L m before becoming vulnerable to fishing. The mesh size of the beach seine needs to be enlarged, as the estimated length of capture was much smaller than all L m values. The results have important management implications for protecting juveniles and mega-spawners of the studied species in Lake Koka and beyond.

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Acknowledgments

The study was financed by the German Academic Exchange Service (DAAD) and the National Fisheries and Aquatic Life Research Center (NFALRC) of the Ethiopian Institute of Agricultural Research (EIAR). NFALRC also provides technical support and logistics for the fieldwork. NFALRC research staffs particularly Mr. Fikadu Tefera, Mr. Getnet Workye, Mr. Essayas Asefa, Mr. Tarekegn Arage, Mr. Alemayahu Wube and Mr. Tsegaye Dadi, and drivers Mr. Birhan Jemal, Mr. Kebede Bereda and Mr. Wolde-Michael Tesfaye  are greatly acknowledged for their assistance during the field work in fish sample and data collection. We are also grateful for the two anonymous reviewers for their constructive comments.

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  1. Leibniz Zentrum für Marine Tropenökologie (ZMT), Fahrenheitstraße 6, 28359, Bremen, Germany

    Gashaw Tesfaye, Matthias Wolff & Marc Taylor

  2. Ethiopian Institute of Agricultural Research-National Fisheries and Aquatic Life Research Center, P.O. Box 64, Sebeta, Ethiopia

    Gashaw Tesfaye

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  1. Gashaw Tesfaye
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Correspondence to Gashaw Tesfaye.

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Tesfaye, G., Wolff, M. & Taylor, M. Gear selectivity of fishery target resources in Lake Koka, Ethiopia: evaluation and management implications. Hydrobiologia 765, 277–295 (2016). https://doi.org/10.1007/s10750-015-2420-0

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