Untitled - CNR

BI (Kg per km 2 )Fishery and Sea Resources3025MEDITSGRUND201510501993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009Figure 3: Pink shrimp Biomass Indices (BI; mean ± sd) from surveys in the Strait ofSicily.mortality rates (F) by size values obtainedby VIT on commercial catch show the typicalpattern of Hake caught by trawling withthe fully exploited size corresponding tosize between 20 and 40 cm TL (age group2-4) (Figure 10). The mean F over 2-4 ageclass was 0.67, whereas that over the sizeforming the whole catch was 0.32.The SSB and YIELD per recruit accordingto fishing mortality by a multiplicative factorof current F, obtained by VIT (Figure11), shows a pattern very similar to that obtainedsimulating the likely changes in Yand SSB per recruit in function of absolutefishing mortality (F) with the YIELD package.According to the steady state VPA on2006 and 2007 commercial data, an overfishingstate is detected. Maintaining thecurrent fishing pattern, a reduction of Fcof 62% is advisable to reach F0.1. Thelong term gain in Y/R consequent to movefrom Fc (F= 0.67) to F0.1 (F=0.46) was estimatedin 11% of the current value (Table4). Comparing recent Fc (0.76 mean over2006-2008) based on trawl surveys data(Figure 11) and the F0.1 (F=0.16) obtainedby YIELD package, a more severe decreaseof fishing mortality, corresponding to 78%,should be implemented to reach an optimalexploitation in long term (Table 5). Thegain in terms of yield should be very high,being about 30% of the current one (from42 to 57 g per recruit).3.3 Red shrimpBiomass indices from trawl surveys showan increasing pattern from 1997 to 2002(Medits data) and a stable pattern in morerecent years (2003-08) (Figure 12). Fishingmortality rates (F) by size obtained byVIT analyses on commercial catches show1994