Lipid reserves of red mullet (&lt;i&gt;Mullus barbatus&lt;/i&gt;) during pre-spawning in the northwestern Mediterranean

Josep Lloret,Montserrat Demestre,Josep Sánchez-Pardo

doi:10.3989/scimar.2007.71n2269

Abstract

SUMMARY: Lipid reserves are a particularly important attribute of fishes because they have a large influence on growth, reproduction and survival. This study analyses the lipid content of red mullet (Mullus barbatus) pre-spawners in three different areas of the northwestern Mediterranean in relation to trawling activities and river runoff. The muscle lipid was considered as an indicator of the somatic condition of individuals whilst the gonad lipid was used as a proxy of the energy invested in reproduction. The results show that fish with the highest muscle lipid levels inhabited the area where fishing impact was lowest. Since the abundance and biomass of polychaetes, which represent the main food source for red mullet, were found to be lower in trawled zones than in unfished ones, we suggest that differences in the muscle lipid levels between areas might be attributed to variation in prey abundance in relation to fishing impact. However, no impact of river runoff on lipid reserves of red mullet was observed. The results also show that muscle and gonad lipid reserves are not related to each other during pre-spawning.

Highlights

Lipid reserves are a important attribute of fishes because they have a large influence on growth, reproduction and survival, with inadequate reserves being implicated in the reduced reproductive potential of several fish species through reduced fecundity and quality of eggs and larvae or delayed maturation
The relative lipid content in the gonad decreased with fish length, even though the coefficient of determination was low (r2 = 0.19), whilst the percentage of fat in the dry muscle, the Lipid Musculosomatic index (LMSI) and the Lipid Gonadosomatic index (LGSI) were size-independent within the size ranges of the fish analysed (p>0.05)
We suggest that red mullets are fatter in the Valencia area because the lower fishing impact there allows a greater abundance and biomass of polychaetes, as has been demonstrated in the study carried out in the Ebre area

Summary

Introduction

Lipid reserves are a important attribute of fishes because they have a large influence on growth, reproduction and survival (reviewed by Shulman and Love, 1999), with inadequate reserves being implicated in the reduced reproductive potential of several fish species through reduced fecundity and quality of eggs and larvae or delayed maturation (reviewed by Lambert et al, 2003). Body fat content affects the maturity, spawning and egg quality of many fish species; a deficiency can negatively affect gonad development, fecundity, fertilisation and. Starvation due to exhaustion of energy reserves, during the non-feeding and reproductive periods, weakens fishes and renders them more susceptible to predation, diseases and a variety of environmental stressors (Shulman and Love, 1999). The accumulation of sufficient energy reserves is important to safeguard the future population success of harvested species and to guarantee the viability of other animals feeding on them, including top predators (Wanless et al, 2005)

Objectives

Methods

Results

Discussion

Conclusion