Life cycle traits and stock assessment of Pegusa impar (Bennett, 1831) in the shallow coastal waters of Southwest Sicily

Abstract

       From spring 2002 to winter 2011 a catch-effort survey was conducted in the wide Gulf between Cape San Marco and Cape Granitola (southwest coast of Sicily). The target fleet was the small scale fishery, using trammel net and gill net, based in the port of Marinella di Selinunte located in the centre of the Gulf. From 2005 to 2008 seasonal statistically significant samples of the catch of Pegusa impar (BENNETT, 1831) Adriatic sole were purchased to study the life history. The growth parameters of the Von Bertanlaffy model were estimated: L_∞ = 249 mm, k = 0.25 year^-1, t₀ = - 2.0 year for females; L_∞ = 250 mm, k = 0.26 year^-1, t₀ = - 1.8 year for males. The maximum estimated age by whole otolith was 6 + years old. The parameters a and b of the length-weight relationship were estimated a = 0.000007 and b = 3.0562 for females and a = 0.000008 and b = 3.0157 for males. Length at first sexual maturity was 155.82 mm and 156.22 mm for females and males respectively. Age at first sexual maturity was 1.99 years for females and 2.57 years for males. The spawning period lasts throughout spring and summer with a migration from greater depths into shallow waters. The most exploited length class was 160 mm through 2007 but in 2008 it became 150 mm. The yearly catch ranged from 842 Kg and 9,743 specimens to 2,703 Kg and 65,345 specimens. The annual fishing effort ranged from 3,142 Km of gear at sea to 6,017 Km of gear at sea. Stock assessment was carried out in the frame of the Schaefer model using FMSP-CEDA software. The Maximum Sustainable Yield, the Carrying capacity, the Catchability coefficient, the Intrinsic population growth rate and the Replacement yield were respectively 2,140 kg, 7,132 kg, 0.000055 kg, 1.200 and 1,869 kg. The biomass trend predicted to 2020 shows that if after 2011 fishing effort increases by ten percent year by year, the resource will begin to decline beginning in 2013. Although the present data do not indicate that the resource is currently in overexploitation, it is however necessary not to increase fishing effort.