Naslov
Anchovy and sardine stock assessment in the GSA 17: 1975-2007

Autori
Santojanni, A. ; Cingolani, N. ; Donato, F. ; Colella, S. ; Belardinelli, A. ; Giannetti, G. ; Leonori, I. ; Sinovčić, Gorenka ; Marčeta, B.

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Skup
GFCM-SAC-SCSA

Mjesto i datum
İzmir, Turska, 22.09.2008. - 26.09.2008

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
anchovy; sardine; Adriatic Sea; shared stocks; population dynamics methods; Virtual Population Analysis

Sažetak
Anchovy (Engraulis encrasicolus, L.) and sardine (Sardina pilchardus, Walb.) are between the most important commercial species of the Adriatic Sea. The present assessments are based on time series of data from 1975 to 2007. Catch and fishing effort data have been collected since 1975. Biological data have been collected as well: length frequency and age-length data were combined to obtain annual catch-at-age series, which represent the basic input of VPA. For anchovy, the annual natural mortality rates M = 0.6 were employed for VPA calculations ; according to a precautionary approach, more emphasis was given to the results obtained with M = 0.6. For sardine, M = 0.5 was selected.The Laurec-Shepherd tuning of VPA (Darby and Flatman, 1994) was performed using abundance index series derived from echo-survey carried out from the midline to the western side of Adriatic. The average stock biomass of anchovy estimated using M = 0.6 was around 120000 tonnes in the period 1976-2007 in the recent period 2005-2007. The corresponding average total catches were equal to 27890 (whole period) and 42614 (recent period) tonnes, respectively. The most recent values of the exploitation rate of anchovy stock, obtained using M = 0.6 and unweighted F0-3 (with the “ initial” age distribution in the tuning data), were lower than the threshold 0.4. The stock biomass of anchovy dropped at a very low level in 1987. After this collapse, recovery took place, but fluctuations still occurred, in particular in recent years. It should be remembered that strong changes over time are commonly observed in the abundance of small pelagics, in particular anchovies (Jacobson et al., 2001). The recent exploitation rate, 0.28 was under the Patterson’ s threshold, but on the other hand, an increase was observed in both western and eastern side catches of most recent years: the mentioned average for the period 2005-2007, 42614 tonnes, was quite over the average for the previous years from 1995 to 2004, 27353 tonnes. The stock can be considered as fully exploited. The average stock biomass estimated for sardine was around 440000 tonnes in the period 1975-2007, whereas it was around 90000 tonnes in the recent period 2005-2007. The corresponding average total catches were equal to 44439 and 17489 tonnes, respectively. The most recent values of the exploitation rate of sardine stock, obtained using unweighted F0-5, were higher than the Patterson’ s threshold 0.4. Moreover, a strong decline of stock biomass occurred after the peak in the first half of 1980s ; this decline was continuous till the end of 1990s: then, biomass was quite stable around values slightly lower than 100000 tonnes, which corresponded to the lowest abundance of the time series. The stock can be considered as overexploited.

Izvorni jezik
Engleski

Znanstvena područja
Biotehnologija

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