NOMINAL CATCH RATES FOR CANADIAN BLUEFIN TUNA IN 2006

Transcription

1 SCRS/2007/33 Collect. Vol. Sci. Pap. ICCAT, 62(4): 2-7 (2008) NOMINAL CATCH RATES FOR CANADIAN BLUEFIN TUNA IN 2006 S.D. Paul, S. Smith and J.D. Neilson SUMMARY Updated nominal catch rates are presented for Canadian bluefin tuna fisheries in the Gulf of St. Lawrence ( ) and off Southwest Nova Scotia ( ) based on data from commercial log records. Spatial distribution of the fisheries was generally consistent in 2006 with those observed in 200. Reports from industry indicate that conditions were favourable for bluefin tuna fishing in Canadian waters during the 2006 season, with the exception of the trap fishery. The nominal CPUE in the Gulf of St. Lawrence declined in 2006, though remained at a relatively high level. Nominal CPUE in southwest Nova Scotia remains unchanged from 200. It is suggested that the nominal catch rate indices may serve as appropriate provisional indicators of abundance during years when no stock assessment is conducted. RÉSUMÉ Les taux actualisés de capture nominale sont présentés pour les pêcheries canadiennes de thon rouge qui opéraient dans le Golfe du St Laurent ( ) et au sud-ouest de la Nouvelle Ecosse ( ) en se fondant sur les données des registres commerciaux. En général, la distribution spatiale des pêcheries en 2006 coïncidait avec celle observée en 200. Les rapports de l industrie indiquent que les conditions étaient favorables à la pêche de thon rouge dans les eaux canadiennes au cours de la saison de 2006, à l exception de la pêcherie de madragues. L CPUE nominale dans le Golfe du St Laurent a chuté en 2006, bien qu elle soit demeurée à un niveau relativement élevé. La CPUE nominale dans le sud-ouest de la Nouvelle Ecosse demeure inchangée par rapport à 200. Il est suggéré que les indices du taux de capture nominale peuvent servir d indicateurs provisoires appropriés de l abondance pendant les années où aucune évaluation de stock n est réalisée. RESUMEN Se presentan las tasas de captura nominal actualizadas para las pesquerías de atún rojo canadienses en el Golfo de San Lorenzo ( ) y frente a Nueva Escocia sudoccidental ( ) basadas en datos de los registros comerciales. La distribución espacial de las pesquerías era generalmente coherente en 2006 con la observada en 200. Los informes de la industria indican que las condiciones fueron favorables para la pesca del atún rojo en aguas canadienses durante la temporada de 2006, con la excepción de la pesquería de almadrabas. La CPUE nominal en el Golfo de San Lorenzo descendió en 2006 aunque permaneció a un nivel relativamente alto. La CPUE nominal en Nueva Escocia sudoccidental permanece sin cambios desde 200. Se sugiere que los índices de las tasas de captura nominal podrían servir como indicadores provisionales adecuados de la abundancia en los años en que no se realiza una evaluación de stock.. Introduction KEYWORDS Tuna fisheries, Catch rates An update of Canada s nominal bluefin tuna catch rate indices and fishery information is provided for the Gulf of St. Lawrence (age 3+, ) and southwest Nova Scotia (ages 7-3, ). The standardized CPUE index for the southwest Nova Scotia series presented at the last stock assessment was confounded by the presence of catch and effort data without an associated catch area in the years , St. Andrews Biological Station, Fisheries and Oceans Canada, 3 Brandy Cove Road, St. Andrews, NB EB M2, Canada, PaulSD@mar.dfo-mpo.gc.ca. 2

2 which influenced input data selection properties for the index (Neilson et al., 2007). Although the matter was not considered to negatively impact the stock assessment, it has been rectified in The updated nominal catch rate series for southwest Nova Scotia include corrected data from 2002 to Description of the Fisheries Canadian bluefin tuna fisheries currently operate in several geographic areas off the Atlantic coast from July to November when bluefin tuna have migrated into Canadian waters (Figure ). The main commercial fisheries occur off the coast of Nova Scotia (Hell Hole rod and reel/tended line, Bay of Fundy harpoon, St. Margaret s Bay trap, Canso rod and reel, and Halifax rod and reel/tended line), in the southern Gulf of St. Lawrence (tended line/rod and reel) and sporadically along the western edge and central region of the Grand Banks (tended line/rod and reel). In addition, bluefin tuna are caught by longline off the coast of Nova Scotia, the Hell Hole and sporadically throughout the Scotian Shelf. The fishery in the southern Gulf of St. Lawrence in 2006 had a similar spatial distribution to that observed in 200 (Figure 2). The fishery typically is conducted in waters north of Prince Edward Island and west of Cape Breton Island. In southwest Nova Scotia during 2006, fleets operated in a similar manner as in 200, however, there was less emphasis on fishing the Hell Hole/northeast Georges Bank area and more along the coast of southwest Nova Scotia where bluefin tuna were reported to be abundant. In addition, there was some fishing activity along the northeast coast of Cape Breton Island in 2006 (Figure 3). During an informal telephone survey, industry representatives generally felt that relative abundance in 2006 had increased, with the exception of the St. Margarets Bay trap fishery which has experienced a decline in bluefin tuna catches over the past several years. The Gulf of St. Lawrence fishery occurred quickly in 2006, and fishermen reported that size and condition of bluefin tuna remained unchanged from 200. Newfoundland representatives cited numerous bluefin tuna on the southwest Grand Banks in All indications, with the exception of the trap fishery, were favourable for bluefin tuna fishing in Canadian waters during the 2006 season. Anecdotal reports from the Gulf of St. Lawrence fishery in 2007 indicate extremely high catch rates. 3. Nominal catch series The Gulf of St. Lawrence nominal CPUEs increased from 996 through Catch rates rapidly increased in 2004, and then slightly declined in 200. The decline continued in 2006, however, CPUE remains at a high level. Nominal catch rates in southwest Nova Scotia increased from the lowest point in the series in 2000 until 2004 when CPUE declined to a level consistent with that experienced throughout the 990 s. In 200, CPUE increased slightly and leveled off in The standardization process has had a minimal effect on the nominal CPUE trend in the past (Neilson et al., 2007), suggesting that the nominal catch rate indices may serve as appropriate provisional indicators of abundance. References ANON Report of the 2006 Atlantic Bluefin Tuna Stock Assessment Session. Collect. Vol. Sci. Pap. ICCAT, 60(3): NEILSON, J.D., S. D. Paul and M. Ortiz Indices of stock status obtained from the Canadian bluefin tuna fishery. Collect. Vol. Sci. Pap. ICCAT, 60(3):

3 0 49 southern Newfoundland 47 Gulf of St. Lawrence New Brunswick P.E.I. 4 Nova Scotia Cape Breton Island Canso Grand Bank USA Halifax St. Margarets Bay Bay of Fundy 42 Hell Hole Georges Bank Figure. Canadian Atlantic Zone, showing geographic location of provinces (bold), major fishing locations and the border between Canada and the USA (solid line). 4

4 Figure 2. Canadian bluefin catch (numbers) in the Gulf of St. Lawrence by tended line and rod and reel. Log record data are aggregated by minute rectangles for the 200 (top), shown in comparison to the 2006 distribution (bottom).

5 Figure 3. Canadian bluefin catch (numbers) off southwest Nova Scotia by tended line, rod and reel and electric harpoon. Log record data are aggregated by minute rectangles for 200 (top), shown in comparison to 2006 (bottom). 6

6 Nominal CPUE (fish per 0 hours) Figure 4. Nominal CPUE index (fish per 0 hours) for the Gulf of St. Lawrence fishery, CPUE (fish per 0 hours) Figure. Nominal CPUE index (fish per 0 hours) for the southwest Nova Scotia fishery,