Temperature and body size affect recruitment and survival of sandeel across the North Sea

Abstract

Climate effects on marine fish depend on life stage, particularly when life stages differ in habitat utilization. In the present study, we investigated life stage-dependent responses of lesser sandeel (Ammodytes marinus) to temperature at contrasting geographical scales. We related population density and individual growth to temperature and found different temperature responses between the first and the second years of life. During the first year of life, fish size was the single most important factor influencing sandeel abundances, indicating a positive relationship between growth and survival. In contrast, during the second year of life, autumn bottom temperature was negatively correlated with sandeel abundance, suggesting elevated mortality in warm years. Southerly areas, experiencing higher temperatures in general, were also the areas showing the strongest response to temperature. This study sheds light on how warming impacts population dynamics of one of the most important forage fishes in the North Sea and supports the discussion of underlying mechanisms.

Get up early: Revealing behavioral responses of sandeel to ocean warming using commercial catch data

“…Although, initial investigations leading to the current study explored the latter (Henriksen, 2020), it was considered outside the framework of this paper. In support of the bioenergetics hypothesis, previous studies have demonstrated relationships between recruitment survival and size of age 0 fish (Foy & Paul, 1999; Henriksen et al, 2021), and both theoretical and experimental work have demonstrated accelerated reserve depletion during warm winters (van Deurs, Hartvig, et al, 2011; Wright et al, 2017).…”

Environmental DNA reveals fine scale spatial and temporal variation of prey species for marine mammals in a Scottish marine protected area

“…Abundances vary throughout the foraging season which would account for the dietary plasticity exhibited by these whales (Robinson et al, 2023). Sandeels were most abundant during June and July, when they are foraging in the water column, but declined from August onwards, when they return to burrows in the sediment (Henriksen et al, 2021) (Figure 2.5). Meanwhile, clupeids were most abundant in June and September.…”

Early ontogeny of the lesser sandeel (Ammodytes marinus)

“…These schools form bridging structures that likely play an important role in their ecology and prevent post‐settled juveniles from being disconnected from suitable bottom substrate 22 . The strong selectivity for areas with specific granulometry represents a habitat limitation that increases the vulnerability of the sandeel to climate change, high fishing pressure, and anthropogenic activity that degrades or eliminates their habitat 10,22‐26 …”

“…22 The strong selectivity for areas with specific granulometry represents a habitat limitation that increases the vulnerability of the sandeel to climate change, high fishing pressure, and anthropogenic activity that degrades or eliminates their habitat. 10,[22][23][24][25][26] These specific sandy habitats are also important for the early life stages of sandeel because they spawn a single batch of demersal eggs that adheres to the sand in an oxygen-rich environment. [24][25][26] After a long (1 month) embryonic period, larvae hatch and drift with the current in the deep layer.…”

“…10,[22][23][24][25][26] These specific sandy habitats are also important for the early life stages of sandeel because they spawn a single batch of demersal eggs that adheres to the sand in an oxygen-rich environment. [24][25][26] After a long (1 month) embryonic period, larvae hatch and drift with the current in the deep layer. After metamorphosis, juveniles congregate and settle in the same areas where the adults are found.…”