Trends of anchovy (<i>Engraulis encrasilocus</i>, L.) biomass in the northern and central Adriatic Sea

Abstract

SUMMARY: Anchovy (Engraulis encrasicolus, L.) is one of the most important commercial species of the northern and central Adriatic Sea. The mean annual catch of anchovy estimated by IRPEM for these areas, in the time interval , is equal to 25,000 tonnes. Estimates of anchovy stock biomass at sea in the time interval 1975-1996 were obtained using two population dynamics methods based on different data inputs: Virtual Population Analysis (VPA) and the DeLury model with recruitment index. VPA was carried out tuning the estimated fishing mortality rate at age by fitting on corresponding Catch Per Unit of fishing Effort (CPUE). Both VPA and the DeLury model yielded sensible results. The effect on the assessments due to the use of a different birth date and thus of split-year data was investigated. Biomass values as well as patterns over time so estimated were similar on the basis of both assessment methods and calendar year versus split-year data. In particular, the biomass in more recent years (around 100,000 tonnes) was lower than in the second half of the 1970s and first half of the 1980s (over 200,000 tonnes). The minimum value (lower than 50,000 tonnes) was always estimated in 1987, when a strong drop in the catch and crisis of the anchovy fishery took place. Though high values of both fishing effort and fishing mortality/exploitation rate were obtained for some years before 1987, very low levels of recruitment in 1986 and 1987 seem to be mainly responsible for the collapse of the stock.

Application of a bioeconomic model for supporting the management process of the small pelagic fishery in the Veneto Region, northern Adriatic Sea, Italy

“…Based on money generated in the market module, fishermen can increase the capital invested in fishing. The outputs Sinovcić (1984Sinovcić ( , 1986Sinovcić ( , 2000, Santojanni et al (2003) are effort (within a system where maximum effort is established by law) and catchability, which the fishermen can affect by investing capital in the vessels. The dynamics of catchability (q t,v ) of each vessel were modelled by considering a conservative interannual 1% (τ) increase in fishing power (Eide et al, 2003) related to the increase in investment of the vessels:…”

“…The von Bertalanffy growth parameters, length-weight relationship parameters, maturity ratio and natural mortality (M) were taken or derived from information on the FishBase website (http://www.fishbase.org/home.htm) and from literature sources (Sinovcic´, 1984(Sinovcic´, , 1986(Sinovcic´, , 2000Santojanni et al, 2003). The necessary information on the population structure concerning the number of individuals, fishing mortality (F) and number of recruits (R) were estimated by means of virtual population analysis using the VIT program (Lleonart and Salat, 1997).…”

“…Small pelagic fisheries play significant economic and social roles in the total value of catches and the number of fishermen employed within the industry. These two small pelagic species have shown important fluctuations in abundance over the last 30 years in the northern and central Adriatic Sea (area 17 of the General Fisheries Commission for the Mediterranean), with a near-collapse of the anchovy stock in the late 1980s (Santojanni et al, 2003;2007a) and a steady decline of the sardine stock in recent years (Santojanni et al, 2005;2007b). Although large fluctuations of small pelagics stocks are well-known and environmentally-driven in many cases (Patterson, 1992;Cushing, 1996), in the case of anchovy and sardine of the northern and central Adriatic, the values of fishing mortality were outside precautionary levels, coinciding with the periods of near-collapse of stocks (Santojanni et al, 2007a, b).…”

“…From an economic point of view fisheries are managed through subsidies, taxes and penalties (AdriaMed, 2005). Sardine (Sardina pilchardus) and anchovy (Engraulis encrasicolus) are the most important species of small pelagic stocks within the Adriatic Sea (Santojanni et al, 2003;2005). Small pelagic fisheries play significant economic and social roles in the total value of catches and the number of fishermen employed within the industry.…”

Stock assessment of sardine (<i>Sardina pilchardus</i>, Walb.) in the Adriatic Sea with an estimate of discards

“…Since 1975 ISMAR has conducted research on the biology and stock assessment of sardine and anchovy in the northern and central Adriatic using population dynamics methods (Levi et al, 1984;Arneri, 1996;Cingolani et al, 1996aCingolani et al, ,b, 1998Cingolani et al, , 2000Cingolani et al, , 2002Santojanni et al, 2001aSantojanni et al, ,b, 2002Santojanni et al, , 2003. Assessments of Adriatic sardine based on population dynamics methods have also been carried out by Alegría-Hernandez (1984), and Sinovcić (1986Sinovcić ( , 1991, for the eastern Adriatic.…”