Quantifying the influence of geography and environment on the northeast Atlantic mackerel spawning distribution

Abstract

Mackerel (Scomber scombrus) in the northeast Atlantic have shown changes in distribution at certain times of the year, which have impacted their exploitation and management. In this study, mackerel spawning habitat over 21 recent years was characterised using generalised additive modelling, based on spatial egg density data collected every third year during targeted ichthyoplankton surveys. Mackerel spawning distribution was found to depend primarily on geographical variables (coordinates and bottom depth), with preferred spawning locations on the shelf‐edge from the north of the Iberian peninsula to the west of Scotland, with a maximum west of Ireland. Environmental drivers had a lesser influence on egg distribution. Dome shaped relationships were found with temperature and mixed layer depth, with respective optimum at 13°C and around –300 m. The model was used to reconstruct maps of the potential habitat (areas where conditions were suitable, but not necessarily used, for spawning). Little changes were observed over the years in the potential habitat, suggesting that the expansion of the egg distribution (realised habitat) was not triggered by changes in the environmental variables investigated. Little evidence was found for density‐dependent habitat selection. There was a tendency for mackerel to make more use of areas of lesser suitability in years with large stock size (1992 and 2010). This pattern, however, broke down in 2013, when stock size was the highest, as spawning occurred very south and concentrated in the most suitable habitat.

Changing fish distributions challenge the effective management of European fisheries

“…This would indicate an overall northward expansion of the area occupied by species with southern biogeographic affinities within the study area. However, the few northward shifts and decrease in spatial occurrence exhibited by the more temperate species (white anglerfish, blue whiting, mackerel, spurdog) in the southern fringes of the study area may indicate an overall shift (expansion and contraction) in distribution for these temperate species within the study area, consistent with previous reports of northward shifts of both the southern range boundary and the spawning area of mackerel in the northeast Atlantic (Brunel et al ).…”

“…These findings strongly suggest that density‐dependent habitat selection is also occurring, with species increasing and decreasing in abundance expanding and contracting their spatial occupancy respectively, as expected according to the MacCall () basin model. Density‐driven changes in distribution have previously been reported for several species within the area considered in this study (Baudron and Fernandes , Brunel et al , Erauskin‐Extramiana et al ). Although the drivers of distribution changes were not formally addressed in this study, our findings indicate that the distribution of the 19 species considered here is at least partly affected by both changes in areas of suitable habitat (possibly as a result of warming sea temperature) and by changes in abundance (due to reduced fishing) via density‐dependent habitat selection occurring within these areas.…”

Modelling Atlantic mackerel spawning habitat suitability and its future distribution in the north‐west Atlantic

“…This dome‐shaped relationship linking both DEP presence–absence and given‐presence to temperature in our models suggests an optimal thermal window potentially driven by constraints linked to embryo development (Nwosu & Holzlöhner, ; Sapkale, Singh, & Desai, ) and the influence of temperature on adult mackerel distribution, migration and timing of spawning (D’Amours & Castonguay, ; Jansen & Gislason, ; Overholtz et al, ). The range of temperature (10–16.5°C) associated with mackerel DEP, with an optimum around 13–14°C (Figures and), is consistent with those described in models for the north‐east Atlantic mackerel (Bruge et al, ; Brunel, Damme, Samson, & Dickey‐Collas, ) and studies using egg survey data for the north‐west Atlantic mackerel stock (Studholme et al, ).…”

“…We used a long time series of mackerel daily egg production (DEP), derived from the annual research vessel surveys aiming Figures 3and4), is consistent with those described in models for the north-east Atlantic mackerel (Bruge et al, 2016;Brunel, Damme, Samson, & Dickey-Collas, 2017) and studies using egg survey data for the north-west Atlantic mackerel stock (Studholme et al, 1999).…”

Modelling species presence–absence in the ecological niche theory framework using shape-constrained generalized additive models

“…Since 1977, the survey has been conducted every three years between January and July and covers a large area from southern Spain to the north of Scotland, with the aim of estimating the total annual egg production of the western Atlantic mackerel stock ICES (2018); Lockwood et al (1981). The egg presence-absence and abundance data collected during the survey have been used to characterize the spawning habitat of mackerel: see Borchers et al (1997); Bruge et al (2016); Brunel et al (2018). Within the framework of an EU programme (INDICES, EU Study 97/017), the samples collected during the 1998 triennial survey were reanalyzed and eggs and larvae of other fish species were quantified Ibaibarriaga et al (2007).…”