Cod - spawning grounds - North Sea (Gonzalez-Irusta and Wright 2016)

What is it: 

The spawning grounds of Atlantic cod (Gadus morhua) layer has been generated to identify the likely distribution of Atlantic cod spawning in the North Sea, taking account of certain environmental influences. The map key classifies Atlantic cod spawning areas as ‘recurrent’, ‘occasional’, ‘rare’ and ‘unfavourable’.

This layer updates the existing (Coull et al., 1998) spawning map for Atlantic cod (Gadus morhua) also available on NMPi, by providing finer granularity to the likely Atlantic cod spawning areas. The Coull et al., (1998) maps have been used for more than a decade to ensure that appropriate protection is afforded to sensitive areas from disturbance.

The model used to create the layers was designed for use at a regional level and above.

More Information: 

Data was obtained from the North Sea International Bottom Trawl Survey (NS-BTS) (2009-2014) to assess the abundance of cod in spawning stage (CSS). The importance of environmental influences on spawning distribution was then examined using General Additive Models (GAMs). Environmental variables such as depth, slope, distance to coast, springtide (tidal currents), sediment type, temperature and salinity were considered.

Cod were found to prefer areas with temperatures around 5–7°C for spawning and there was a general preference for high salinity waters. Seabed conditions also affected spawning distribution with cod selecting coarse sand and avoiding areas of very high tidal flow. The model prediction was compared with the distribution of cod aggregations during the spawning season reported by fishing boats. Seventy per cent of the aggregations were located in areas classified as occasional or recurrent spawning grounds. The predicted distribution confirmed the widespread occurrence of spawning in the North Sea and showed good agreement with recent and past studies of cod egg distribution, suggesting that nearly all major historical areas of spawning still appear in use today. However, the study also found that the recent recovery of spawning-stock biomass was not uniform across the stock, being centered in the northwest subarea.

This output serves as an update to the existing (Coull et al., 1998) spawning map for Atlantic cod (Gadus morhua) also available on NMPi, by providing finer granularity to the likely Atlantic cod spawning areas.

Publication DOI: https://doi.org/10.1093/icesjms/fsv180