Toothfish


Longline operations of Argentine vessels on the Patagonian shelf are reported in Schiavini et al. (1998). A longline fishery for ling (Genypterus blacodes) and to a lesser extent hake (Merluccius hubbsi) began in 1992, but moved to Patagonian toothfish in 1994. Between 1994 and mid 1995 Schiavini et al. (1998) estimate that 24 million hooks were set in Argentine waters within the southwestern South Atlantic (outside of the CCAMLR area). The main longlining areas were between 54S – 57S and 50W – 67W (toothfish) and between 43S – 50S and 59W – 64W (ling and hake) (Schiavini et al., 1998; Weidner et al., 1999). In 2001 there were six vessels operating in Argentine waters, down from nine vessels in 2000 (Gandini and Frere, 2001), and 19 reported by Schiavini et al. (1998) in the mid-1990s. 

Data reported by Schiavini et al. (1998) were used to estimate the annual number of hooks deployed by the Argentine demersal fleet between 1992 and 1995. According to Schiavini et al. (1998) from December 1993 to 17 July 1995 12 of 19 demersal vessels operating were surveyed. Of these 19 vessels, 17 were manual-set operators and 2 were autoliners. Both autoliners were surveyed and 10 of the 17 manual vessels were surveyed. The autoliners recorded 1920 sets and the manual operators 1921 in the south western Atlantic. If it is assumed that the autoliners set 2000 hooks per set and the manual operators set 10500 hooks per set (as also assumed by Schiavini et al. (1998)) then a total of 3.84 and 20.17 million hooks were set by each vessel type respectively. However, only 10 of 17 manual-set operators were surveyed. Pro-rating the manual-set effort to the whole fleet leads to an estimate of 34.29 million hooks over the 18 month period. Including the autoliners’ effort produces 38.13 million hooks. Thus, the number of hooks set per day is 65068 and the annual number set is 23.75 million hooks. 

As the fishery began as a directed fishery for hake and ling, the total annual hooks for years 1992 and 1993 is set to 23.75 million. From 1994 the fishery also targeted Patagonian toothfish. Schiavini et al. (1998) state that around 64% of the total effort surveyed was in the southern regions of the fishery where Patagonian toothfish is targeted. As such the estimated annual effort from 1994 to 2001 is split into southern (Patagonian toothfish) and northern (hake and ling) regions according to this proportion. Favero et al. (2003) state that around 20 million hooks were set annually during their study period of 1999 to 2001. It is assumed that this level of effort extends from 1996 to 2001. From 2002 to 2007, the implied catch rate of toothfish, averaged over years 1999 to 2001 (316 kg/1000 hks) is used to determine the effort. The annual catch is determined from SAGPyA catch statistics for longline and spread by month according to the monthly landings of toothfish. The monthly effort can be calculated by multiplying the catch rate by the catch. 



Hake and Ling

The effort directed at ling and hake is determined in a similar manner to that of the toothfish fishery. From the method described above, 23.75 million hooks were assigned to years 1992 and 1993 (Schiavini et al., 1998). For 1994 and 1995, this effort was also apportioned into the toothfish longline fishery, with 36% being assigned to ling and hake in more northerly regions. From 1996 to 2001, the ling and hake effort was assumed to be 7.2 million (36% of 20 million hooks; Favero et al. 2000). For years 2002 to 2007, the annual effort was determined by applying the mean catch rate for years 1999 to 2001 (268 kg/1000 hks) to the annual estimated longline catch of ling and hake combined (SAGPyA). The fraction of the annual effort assigned to each month was determined by the monthly catch statistics provided by SAGPyA. 

http://www.sagpya.mecon.gov.ar/


Favero, M., Khatchikian, C.E., Aria, A., Rodriguez, M.P.S., Canete, G. and Mariano-Jelicich, R. 2003. Estimates of seabird by-catch along the Patagonian Shelf by Argentine longline fishing vessels, 1999–2001. Bird Conservation International. 13:273-281.

Schiavini, A., Frere, E., Gandini, P., Garcia, N., Crespo, E., 1998. Albatross-fisheries interactions in Patagonian shelf waters. In: Robertson, G., Gales, R. (Eds.), Albatross Biology and Conservation, Surrey Beatty and Sons, Chipping Norton, pp. 208-213.