Sex-specific vertical movements of spawning atlantic cod in coastal habitats inferred from acoustic telemetry.

Fish spawning location and behaviour can be challenging to detect, especially in deep water. Here we utilise two large acoustic telemetry datasets from western and mid Norway to study the vertical movement dimension of individual Atlantic cod Gadus morhua spawning behaviour in their natural habitats. The datasets comprise ~ 6 million depth detections from 644 sexed, mature cod, collected at seven different Norwegian coastal cod spawning grounds during 2017-2021.

Continuous sound from a marine vibrator causes behavioural responses of free-ranging, spawning Atlantic cod (Gadus morhua).

Marine vibrators are a new technology being developed for seismic surveys. These devices can transmit continuous instead of impulsive sound and operate over a narrower frequency band and at lower peak pressure than airguns, which is assumed to reduce their environmental impacts. We exposed spawning Atlantic cod (Gadus morhua) to sound produced by a prototype, but full-scale, marine vibrator, and monitored behavioural responses of tagged cod using acoustic telemetry.

Large females connect Atlantic cod spawning sites.

The Earth's ecosystems are increasingly deprived of large animals. Global simulations suggest that this downsizing of nature has serious consequences for biosphere functioning. However, the historical loss of large animals means that it is now often impossible to secure empirical data revealing their true ecological importance.

Movement diversity and partial sympatry of coastal and Northeast Arctic cod ecotypes at high latitudes.

Movement diversity within species represent an important but often neglected, component of biodiversity that affects ecological and genetic interactions, as well as the productivity of exploited systems. By combining individual tracking data from acoustic telemetry with novel genetic analyses, we describe the movement diversity of two Atlantic cod Gadus morhua ecotypes in two high-latitude fjord systems: the highly migratory Northeast Arctic cod (NEA cod) that supports the largest cod fishery in the world, and the more sedentary Norwegian coastal cod, which is currently in a depleted state. As predicted, coastal cod displayed a higher level of fjord residency than NEA cod.

Vertebral column deformity in adult wild haddock (Melanogrammus aeglefinus).

This study describes radiological malformations in the vertebral column of adult sexually mature wild haddock, Melanogrammus aeglefinus collected from Masfjorden, Western Norway, in 2014 and 2015. There were seven deformed fish (33% of sampled fish), five with mild deformities and two with severe deformities. The deformity types discovered were lordosis, vertebra body asymmetry, compression, fusion (ankylosis), remodelling, and haemal spine hyperostosis.