Do cod form spawning leks? Evidence from a Newfoundland spawning ground

Abstract

Catch and acoustic telemetry data were used to test three predictions of lekking behaviour in Atlantic cod (Gadus morhua L.) at a small-scale spawning ground (∼25 km2) in Placentia Bay, Newfoundland: (1) that cod form male-skewed aggregations during spawning; (2) spawning arenas occur at consistent sites; and (3) on the arenas, there will be higher proportions of spawning fish. Forty-two fishing sets from 1998 to 2003 indicated male-skewed sets early in the spawning season (April) in 5 of 6 survey years. Male-skewed sets were consistently distributed at depths < 50 m and mostly in one part of the ground. The proportions of spawning females and spent males were significantly higher in male-skewed sets, whereas sets with equal sex ratios had significantly higher proportions of immature males and spent females. In addition, cod of both sexes were significantly larger in male-skewed sets. Telemetric tracking of 25 cod in 2002 and 2003 (12 males, 13 females) indicated that both males and females were highly mobile while present on the spawning ground. Overall, our results add support to the hypothesis that cod employ a lekking mating system.