Blue Whiting Spawning Habitat Forecast

Blue Whiting Spawning Habitat Forecast
logo

Forecast sheet 01-20210118. Issued 18-01-2021, covering the March 2021 spawning distribution.

Prepared by Mark R. Payne, DTU Aqua, Copenhagen, Denmark.

This forecast sheet is the first forecast for the 2021 blue whiting spawning season. An update of this forecast will be issued on or before 12 March 2021. For details, see the Change Log at the bottom of this document.

Forecast

The spawning habitat for March 2021 is expected to be compressed against the continental shelf edge. Minimal spawning on or to the west of Rockall Plateau is expected (Figure 1). In historical terms, the spawning habitat is forecast to be among the most contracted since 1950 (Figure 2).

**Figure 1. Forecast spawning habitat for blue whiting in March 2021.** *Habitat is based on the outputs of an ecological niche model of blue whiting larvae distributions and is converted into a metric of habitat quality, from low to high. The 1000m and 2000m isobaths are added for reference.*

Figure 1. Forecast spawning habitat for blue whiting in March 2021. Habitat is based on the outputs of an ecological niche model of blue whiting larvae distributions and is converted into a metric of habitat quality, from low to high. The 1000m and 2000m isobaths are added for reference.

**Figure 2. Time series of spawning habitat characteristics for the northern blue whiting component .** *The time series of spawning habitat maps (e.g. Figure 1) is converted to an indicator of the relative expanded or contracted form of the habitat sizes and plotted. Historical values as show as bars relative to the 1960-2010 climatology (bars - colouring indicates values above or below the mean), while forecast value is shown as a red dot.*

Figure 2. Time series of spawning habitat characteristics for the northern blue whiting component . The time series of spawning habitat maps (e.g. Figure 1) is converted to an indicator of the relative expanded or contracted form of the habitat sizes and plotted. Historical values as show as bars relative to the 1960-2010 climatology (bars - colouring indicates values above or below the mean), while forecast value is shown as a red dot.

How to Use this Forecast

This forecast should be used as a broad-scale indicator of the expected spawning habitat of blue whiting in the upcoming spawning season. This forecast can be used in planning monitoring activities on this stock (e.g. the International Blue Whiting Spawning Stock Survey (IBWSSS)) and commercial fishing activities.

Background

The spawning distribution of blue whiting can vary substantially from year to year (Figures 3). The dominant feature of these changes is a westward expansion away from the shelf-break region west of the European continental shelf onto the Rockall plateau and Hatton bank region.