Population structure and reproductive parameters of the Longneck croaker, &amp;lt;i&amp;gt;Pseudotolithus typus&amp;lt;/i&amp;gt; (Pisces, Bleeker, 1863) in nearshore waters of Benin (West Africa) and their implications for management

Edmond S Ossoukpe,Francis Kofi Ewusie Nunoo,Hederick Roosevelt Dankwa

doi:10.4236/as.2013.46a002

Abstract

Pseudotolithus typus is one of the two commercially important Sciaenids off Benin nearshore waters mainly fished by beach seining. Unfortunately, since 1994, the production of this species has been decreasing, and increasingly more small-sized fishes are regularly harvested, while little is known about the species’ population structure and its life history. Therefore, population structure, probability of capture and size at first capture were investigated using length-frequency data of 1144 specimens sampled from beach seine hauls over a period of 18 months. A total of 54.3% of this population was immature, confirming the domination of smallsized fishes in the catches. Gonad maturation stages were also examined. Frequency distribution of oocyte size exhibited two cohorts of mature oocytes suggesting two spawning periods per year. Monthly averages of gonado-somatic index confirmed that P. typus spawned twice a year during the major warm season (March - May) and during the transition minor warm to minor cold season in October - November. Length at first capture (L75 = 22.76 cm) was smaller than the length at first sexual maturation (L50% = 23.6 cm) indicating a heavy pressure of the beach seine on this resource. To give each fish the chance of reproducing at least once in its lifetime to recruit into the stock, necessary measures such as the size-limit regulation by gradually increasing beach seine mesh size should be developed. Community-based management of the nearshore fishery could contribute to reducing fishing effort during the reproductive periods from February to May and from October to December each year.

Highlights

Many of the world’s fish populations are overexploited, and probably to meet the fish consumption requirements of the human population (Milton et al, 2002 [1]; Nunoo et al, 2006 [2]; Fazli et al, 2007 [3] and Narges et al, 2011 [4])
The current study presents this information for Pseudotolithus typus to contribute to management and conservation policies for further development of this fishery in Benin
The study of population structure and reproduction of P. typus was performed in the nearshore waters of Benin (West Africa) (Figure 1)

Summary

Introduction

Many of the world’s fish populations are overexploited, and probably to meet the fish consumption requirements of the human population (Milton et al, 2002 [1]; Nunoo et al, 2006 [2]; Fazli et al, 2007 [3] and Narges et al, 2011 [4]). As a source of foreign income, the sub-sector contributed US $12 million to Benin’s total receipts of agricultural non traditional export products in 2008 (INSAE, 2009 [6]). Fish is a preferred source of animal protein in the Beninese diet (approximately 55%), with a consumption of approximately 14.4 kg per person per annum (Direction des Pêches, 2011 [7]). The fish requirement for the population (8 millions, INSAE, 2003 [8]) was estimated to be approximately 96,000 metric tons. The fishery sector supports an informal workforce of 1.5 million people (approximately 18% of the population), which includes fishermen, fish processors and traders, most of whom are women (Anato, 1999 [9])

Methods

Results

Conclusion