Population parameters of Mullus barbatus in Izmir Bay (Aegean Sea), using length frequency analysis

By H. Özbilgin, Z. Tosunoğlu, M. Bilecenoğlu, A. Tokaç. 2004

119 citations recorded by the source corpus.

¼ )0.305, C ¼ 0.27 andWP ¼ 0.45. Potential lifespan was estimated to be 5.3 years.Total mortality (Z) based on the length converted catch curvewas 3.70 (seasonal data) and 3.85 (non-seasonal data).Naturalmortality (M) was 1.07 and the exploitation ratio (0.71–0.72)revealed an overﬁshed stock.IntroductionThe red mullet, Mullus barbatus Linnaeus 1758, is a benthicspeciesinhabitingsandyandmuddybottomsofthecontinentalshelf, with a widespread distribution along the MediterraneanSeacoasts(Hureau,1986).Itshabitatextendsfromtheshallowlittoral zone (especially juveniles) down to 300 m, but is morecommon in depths between 20 and 50 m. In Turkey, the redmulletisofgreatcommercialvalueandisoneofthemaintargetspecies ofthe small- and large-scale ﬁshery. Annual catchesﬂuctuatedduringthelastdecadefrom2450to4774 tonnes;theconsiderable decrease in M. barbatus catch along the Turkishcoasts in the past few years is primarily due to improperﬁsheries management and also to illegal ﬁshing activities.Mullus barbatus was the subject ofseveral growth, repro-duction (Togulga and Mater, 1992; Sahin and Akbulut, 1997;Tu¨reli andErdem, 1997; C¸elik andTorcu,2000) andselectivitystudies along Turkish coasts (Tosunoglu et al., 2003a,b;O¨zbilgin and Tosunoglu, 2003; Tokac¸ et al., 2004). In thispaper, we attempt to improve previous assessments byestimation ofseasonal growth and mortality parameters.MaterialandmethodsSamples were collected during 2002 in monthly intervals atIzmir Bay onboard the R/V Egesu¨f(27 m length, 500 HPengine) by using a conventional bottom trawl with a cod-endmesh size of24 mm. Depth range ofthe ﬁshing ground was25–30 m. Towing speed varied between 2.2 and 2.6 knots, andtowing duration was limited to 45 min for all hauls. A total of95 valid hauls was made, with haul numbers in each month asfollows: January: 4, February: 20, March: 15, April: 15, May:1, June: 3, July: 18, August: 6, September: 7, October: 3,November: 3. The December 2002 sampling was omitted fromthe study because ofinvalid hauls. All ﬁsh obtained weremeasured to the nearest 0.5 cm immediately after capture, andmonthly length–frequency distributions for use in growthestimation were constructed. Since the number ofﬁsh sampledin each month varied, length–frequency distributions werestandardized to express each length class size as a relativefrequency per 1000 ﬁsh. The seasonal von Bertalanﬀy growthfunction (VBGF) was used to estimate growth parameters:L

Subfields: Aquatic Science, Global and Planetary Change, Molecular Biology

View Paper: https://www.semanticscholar.org/paper/7ed55dff0b18b0debfcda381ea34c474a37579eb