Assessment of body size and catch per unit effort of Nile perch (Lates Niloticus) caught using different fishing gears at Magu district in Lake Victoria, Tanzania

Julitha N Nyakibinda,Renalda N Munubi

doi:10.33472/afjbs.2.4.2020.73-83

Abstract

This study was conducted to assess body size distribution and Catch Per Unit Effort (CPUE) of Nile perch (Lates cf. niloticus) captured using three common fishing gears at Magu district in Tanzania. Three landing sites along Lake Victoria were selected for this assessment. Each site was visited twice per week for two months. At each site 10 boats were identified based on the gear used and randomly selected for fish count. Ten fish per boat were taken for weight and length measurements. The results show that the main fishing gears used to catch fish at all sites were gillnet (GN), long line (LL) and beach seine (BS). Mean length of captured fish recorded from each gear were 33.7, 41.5 and 43.8 for beach seine, gillnets and long lines respectively, which was below the minimal required length of 50 cm. Large proportion of small landed fish were observed in vessels fishing with beach seine, this was due to illegal nature of the beach seine, where by fishermen used small mesh sizes of 10 mm to 12 mm. However, beach seine had higher CPUE (kg/gear/day) (44.9) and gillnet had the lowest (22.6). This study revealed that the mean length from all sites were below the legal minimum size required by the Tanzanian government, suggesting that all beaches are involves in over exploration of fish.

Highlights

Nile perch and Nile tilapia were introduced in the Lake Victoria in the 1950s and 1960s with some controversial reasons of their introduction, though many articles describe the introduction as means of increasing fish productivity to improve domestics and region fish production, contribute to food security and employment (Pringle, 2005)
The study revealed that three main gears were used for this study (gillnet (GN), long line (LL) and beach seine (BS)) to catch fish at Nyamikoma, Nyakaboja and Ihale beaches
The length distribution of Nile perch caught using different gear types was slightly different among the sites and indicated that more than 70% of all Nile perch catch were below 50 cm TL (Figure 3)

Summary

Introduction

Nile perch and Nile tilapia were introduced in the Lake Victoria in the 1950s and 1960s with some controversial reasons of their introduction, though many articles describe the introduction as means of increasing fish productivity to improve domestics and region fish production, contribute to food security and employment (Pringle, 2005). The introduction led into enormous expansion of fisheries industries in the 1990s and the establishment of several fish processing plants whereby more than nine processing plants were constructed along the lake shore of Tanzania alone (LVFO, 2013; and Njiru et al, 2009). Between 2000 and 2014 the number of vessels in the inland fisheries almost doubled, from 25,014 to 49,627. Inland fisheries production increased from 271,000 tons to 320,566 tons in 2005 (Matsuishi et al, 2006)

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