Whiting - spawning grounds - North Sea (Gonzalez-Irusta and Wright 2017)
What is it:
The spawning grounds of whiting (Merlangius merlangus) layer has been generated to identify the likely distribution of whiting spawning in the North Sea, taking account of certain environmental influences, with due regard for possible density dependent effects on distribution. The map key refers to the ‘Index of Persistence’ of whiting spawning, where a value of 0 means that that the cell was not classified as suitable for any year during the study period and a value of 1 means that the cell was classified as suitable for all the years studied.
This layer updates the existing (Coull et al., 1998) spawning map for whiting (Merlangius merlangus) also available on NMPi, by providing finer granularity to the likely whiting 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.
Data was obtained from the North Sea International Bottom Trawl Survey (NS-BTS) (2009-2015) to assess the abundance of whiting in spawning stage (WSS). The importance of environmental influences on spawning distribution was then examined using General Additive Models (GAMs). Environmental variables such as depth, distance to coast, springtide (tidal currents), sediment type, temperature, salinity and current velocity were considered. Whiting showed high plasticity in spawning ground selection with extensive areas of the North Sea appearing suitable across the study period. Nevertheless, a divide between two centres of persistent spawning aggregation was found consistent with the boundary described in previous studies. In addition to aggregations suggested by past egg surveys, another spawning area off the north east Scottish coast was identified. The study identified springtide as a key physical determinant of whiting spawning distribution, which may be linked to the need for larvae to be advected offshore.
Contrary to past studies, peak abundance of whiting was found around 125 m bottom depth, although there may have been differences in physical preferences related to the region of the North Sea studied. The persistence of some spawning aggregations of whiting indicates the need for marine spatial planning to consider the potential impact of marine developments in these areas.
This output serves as an update to the existing (Coull et al., 1998) spawning map for whiting (Merlangius merlangus) also available on NMPi, by providing finer granularity to the likely whiting spawning areas.
Publication DOI: https://doi.org/10.1016/j.fishres.2017.07.005