Rebuilding Atlantic cod: Lessons from a spawning ground in coastal Newfoundland

Rebuilding Atlantic cod: Lessons from a spawning ground in coastal Newfoundland

G.A. Rose, I.R. Bradbury, B. deYoung, S.B. Fudge, G.L. Lawson, L.G.S. Mello, D. Robichaud, G. Sherwood, P.V.R. Snelgrove, and M.J.S. Windle

Rebuilding Atlantic cod: Lessons from a spawning ground in coastal NewfoundlandThis is part of Resiliency of Gadid Stocks to Fishing and Climate Change
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Description

Atlantic cod (Gadus morhua) was studied at the Bar Haven, Placentia Bay, Newfoundland (NAFO 3Ps stock unit) spawning ground from 1996 to 2003. Lessons applicable to management of rebuilding stocks derived
from these studies are reviewed: (1) cod spawn in the same area each year, but numbers and timing vary (spawning biomass varied from 2,000 to 25,000 t, with timing protracted over at least 100 days); (2) courtship and spawning behavior is complex, and includes lekking, sound production, and vertical rituals; (3) large fish in good condition are necessary to large egg potential because fecundity increases exponentially with fish size—total egg potential varied considerably from year to year with spawning abundance, age changes, and mean liver condition in spawning females; (4) retention of early life stages did not explain local recruitment and rankings of annual densities of eggs, larvae and juveniles did not match with local recruitment during three years of study; (5) dispersal of early life stages, juveniles, and adults was density-dependent; (6) individual adults homed to the same spawning ground in sequential years, but others strayed; (7) egg potential was correlated with the return of adults to the spawning ground 4-5 years later (r2 = 0.33, d.f. 3), and with recruitment to the full stock area (NAFO subdivision 3Ps) (r2 = 0.96, d.f. 5), with only weak compensation in survival at low stock size; (8) fishing on spawning aggregations may harm reproductive potential; and (9) seasonal fisheries influence fishing mortality, commercial yield, and value. Management implications are discussed.

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