Research Document - 2005/056

Atlantic mackerel (Scomber scombrus L.) fishery, biology, diet composition and predation in NAFO Subareas 3 and 4 in 2004

By Grégoire, F., C. Savenkoff

Abstract

In 2004, landings of Atlantic mackerel (Scomber scombrus L.) in the northwest Atlantic totalled 87,980 t, up to 8,489 t from 2003. In eastern Canada, 35,023 t were landed, including 32,966 t in Newfoundland only. The actual landings of 2004 should be higher since landings data from Prince Edward Island, New Brunswick, and Nova Scotia have not yet been accounted for. On the west coast of Newfoundland, the most important catches were realized in unit areas 4Rb (2,478 t), 4Rc (11,426 t), and 4Rd (7,492 t) in comparison with 3Kd (1,029 t) and 3Kh (10,123 t) for the east coast. Mackerel catches of this importance is unusual for the east coast of Newfoundland. The other important unit areas were 4Tf (966 t) and 4Xm (2,288 t) located respectively in the Magdalen Islands and close to Halifax, Nova Scotia. Since 2000, the most striking feature of commercial mackerel catches has been the presence of a high abundance and very large proportion of fish from the 1999 year-class. Over the past five years, this year-class has accounted for between 56% and 77% of the total number of fish caught, which hasn’t been seen since the late 1960s. In 2004, one- and two-year age groups were also predominant in fall catches made in the Southern Gulf of St. Lawrence (using lines) and on the East coast of Newfoundland (using purse seines). The presence of small mackerel in the latter area is unusual. Data collected in the mid-1980s showed that mackerel in the Northern Gulf of St. Lawrence fed mainly on small (< 5 mm) and large (≥ 5 mm) zooplankton. As shown by the results of a model of the Northern Gulf of St. Lawrence marine ecosystem, the main causes of mortality for mackerel in the mid-1980s were cetaceans, large cod (Gadus morhua), and large demersals. The proportion of mackerel making up the cetacean and large cod diets during this period was 18.7% and 1.5% respectively. The same model showed that fishery related mortalities gradually increased from 2% in the early 1980s to 15% in the mid-1990s, and finally to 27% in the early 2000s.

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