Fine-scale diel and gender-based patterns in behaviour of Atlantic cod (Gadus morhua) on a spawning ground in the Western Gulf of Maine

Abstract

Understanding the influence of spawning behaviour on the fine-scale distribution of Atlantic cod is essential to the design of effective conservation measures. Laboratory studies suggest that spawning activity occurs primarily at night, yet no field studies have evaluated the influence of diel period on the behaviour of individual wild spawning cod. Using an acoustic telemetry positioning system, the fine-scale movements of spawning cod were observed in situ as they returned to the same spawning location over consecutive seasons. The resulting data identify clear gender-based diel patterns in space use and aggregation behaviour among cod on a spawning ground. During the day, females remained aggregated in one small location that varied little within and between years. Males also aggregated during the day, but occupied a much larger adjacent area. At night, individual males sought out separate small territories while females generally remained near their daytime aggregation site, making periodic excursions into the surrounding area. These patterns were surprisingly stable over the 2 years of observation, indicating little interannual variability in spawning behaviour. This study provides an unprecedented examination of the natural spawning behaviour of Atlantic cod, and makes connections between earlier laboratory studies and field observations.

Aquatic animal telemetry: A panoramic window into the underwater world

“…Telemetry has allowed accurate estimation of the horizontal space use of a diverse range of organisms from Atlantic cod (Gadus morhua) ( Fig. 2A) (19) to king prawns (Penaeus plebejus) (20). At localized scales, these data have defined home ranges and core habitat use, delineated species distributions, and identified spawning site fidelity.…”

Use of otolith quality flags to assess distributional dynamics in Baltic cod stocks

“…Sex and length class did not affect differences in the proportion of quality-flagged otoliths. In cod, behavioural differences between sexes are minor (Neuenfeldt and Beyer 2003;Neuenfeldt et al 2007), except for fine-scale patterns during the spawning period (Nielsen et al 2013;Dean et al 2014). Therefore, in any given area, female and male cod most likely experience largely the same hydrographic conditions, which results in similar readability patterns.…”

Depth and temperature associations of haddock Melanogrammus aeglefinus off southern Newfoundland

“…An additional aspect of this research was to explore potential differences in M. aeglefinus habitat associations in relation to sex and maturity status. A number of gadoids including Atlantic cod Gadus morhua L. 1758 and M. aeglefinus have been hypothesized to segregate sexually during the spawning season with mature males aggregating in areas where individuals possibly defend small territories and females only venturing into these areas when ready to engage in courtship and spawning (Morgan & Trippel, ; Hawkins & Amorim, ; Nordeide & Folstad, ; Dean et al ., ). Contrary to expectation, little evidence was found for differences in habitat use between males and females or immature and mature fish.…”