Studies of dietary preferences of migratory species are of great importance as these species connect food webs of habitats across the migration route and thus represent trophic relationships between the spatially disjointed communities. Here we described the dietary preferences of threespine stickleback G. aculeatus in the White Sea during the spawning season using stable isotope and stomach content analyses. The two analyses suggested that during the spawning season, when sticklebacks spend the majority of their time inshore, their diet consists mostly of benthic species, while at the beginning of the spawning season when fish migrating from the offshore were feeding on plankton. Additionally, we demonstrated that stickleback eggs contributed greatly to the diet of both male and female fish. Using Bayesian mixing modeling, we showed that dietary preferences in females were broader than in males, and more variable during the spawning season. While guarding their nests, males fed almost exclusively on eggs. Both stomach contents and isotope signatures demonstrate that by the end of the spawning season sticklebacks again increase the consumption of plankton. Isotope analysis proved to be a more reliable tool to trace this change than stomach content analysis. Our results show that stable isotope and stomach content analyses are complementary in understanding seasonal changes in the dietary composition of stickleback.

The spatial and temporal variability in the dietary preferences of juvenile three-spined stickleback Gasterosteus aculeatus were studied across the typical coastal habitats of Keret Archipelago, Kandalaksha Bay(the White Sea). The sampling of fish using a beach seine was conducted in the late July–early August period and in late August. Additionally, zooplankton samples were collected to conduct a quantitative assessment of the abundance of potential prey items. The similarity percentage (SIMPER) analysis was applied to the data obtained from the stomach content and revealed the five planktonic taxa most prominently contributing to the diet of juvenile sticklebacks. Among these, the copepod Temora longicornis was the most important prey item at marine sites, while Acartia longiremis dominated the diet of fish in the marine lagoon. The calculation of the selectivity index revealed that some taxa (such as A. longiremis) were always avoided by juvenile fish, whereas the selectivity of some taxa increased in late August. In general, juvenile sticklebacks demonstrated a pronounced individual variation in their selectivity, even when a particular prey item was selected positively during the whole period of study. Our data highlight that despite the predominant consumption of easily available prey by juvenile sticklebacks, they demonstrate taxonomic- and size-specific prey selectivity.

Great Antarctic expeditions, seal hunting and whaling industries left a legacy in natural history collections. To provide the basis for analysing the impact of whaling on marine ecosystem structuring, we conducted bulk isotope analysis from specimens of baleen whales ( Balaenoptera musculus and Balaenoptera physalus ) and seals ( Arctocephalus australis and Hydrurga leptonyx ) collected between 1843 and 1951 from the South Atlantic, Patagonian waters, Southern Ocean and Antarctic coastal seas, and preserved in the collection of Natural History Museum, London. Analysis of this material indicates the pre-whaling state of these environments and changes in the trophic position (TP) of whales and seals during the period of extensive human pressure. Being controlled for the Suess effect, δ ¹³ C values in B. musculus , B. physalus and H. leptonyx varied during the period of industrial-scale whaling. Bone collagen δ ¹⁵ N values and corresponding TP indicate possible trophic changes in A. australis and variability of the foraging areas of B. musculus . This study highlights the use of museum specimens for tracing historical trends associated with changes in the population structure and distribution of species, indicating long-term variability in their foraging ecology. This article is part of the theme issue ‘Shifting seas: understanding deep-time human impacts on marine ecosystems’.

Arctica islandica is a long-lived marine bivalve mollusc that inhabits the continental shelf seas of the North Atlantic Ocean at subpolar and temperate latitudes. Growth increments formed within A. islandica shells can be analysed to form annually resolved and absolutely dated sclerochronologies that are considered the marine counterpart to dendrochronologies. Here, we present an updated A. islandica chronology from the Fladen Ground (North Sea) that spans between CE 1410 and 2021. The A. islandica chronology significantly ( p  < 0.05) covaries with observational local sea surface productivity, subsurface seawater temperature and sea surface salinity. These analyses highlight the potential sensitivity of the chronology to the variability in the regional seawater temperature and salinity, and atmospheric circulation patterns (wind stress and the summer North Atlantic Oscillation). The connection between the atmospheric circulation patterns and A. islandica shell growth is likely due to fluctuations in the strength of the Atlantic inflows into the North Sea and local mixing. This highlights the significant potential in using A. islandica records to provide long-term baselines of North Sea marine dynamics. These baselines are critical for understanding the impact future changes in regional oceanic and atmospheric variability may have on North Sea ecosystems and fisheries. This article is part of the theme issue ‘Shifting seas: understanding deep-time human impacts on marine ecosystems’.

Studies of dietary preferences of migratory species are of great importance as these species connect food webs of habitats across the migration route and thus represent trophic relationships between the spatially disjointed communities. Here we describe dietary preferences of threespine stickleback G. aculeatus in the White Sea during the spawning season using stable isotope and stomach content analyses. Both analyses indicated that during the spawning season, when sticklebacks spend most of the time in the inshore, their diet significantly consist of benthic species in contrast to the start of the spawning season when fishes migrating from the offshore are feeding on zooplankton. Also, we show that stickleback eggs contribute greatly to the diet of both male and female fishes. Using Bayesian mixing modelling we show that dietary preferences in females were broader than in males, and more variable during the spawning season. Males fed on eggs almost while guarding their nests. Both stomach contents and isotope signatures demonstrate that by the end of the spawning season sticklebacks again increase consumption of plankton, and isotope analysis proved to be more reliable tool to trace this change than stomach content analysis. Our results show that stable isotope and stomach content analyses well supplement each other in understanding of seasonal changes in dietary composition of stickleback.

Great Antarctic expeditions, seal hunting and whaling industries left a legacy in natural history collections. To provide the basis for analysing the impact of whaling on marine ecosystem structuring, we conducted the bulk isotope analysis from the specimens of baleen whales ( Balaenoptera musculus and B. physalus ), and seals (Arctocephalus australis and Hydrurga leptonyx ) collected between 1843 to 1951 from the South Atlantic, Patagonian waters, Southern Ocean and Antarctic coastal seas, and preserved in the collection of Natural History Museum, London. Analysis of this material indicates the pre-industrial whaling state of these environments, and changes in the trophic position of whales and seals during the period of extensive human pressure. Having controlled for the Suess effect, δ ¹³ C values in B. musculus , B. physalus and H. leptonyx were different before and after the onset of industrial-scale whaling (1904). Bone collagen δ ¹⁵ N values and corresponding trophic position indicate possible trophic changes in A. australis, and variability of the foraging areas of B. musculus . This study highlights the use of museum specimens for tracing historical trends associated with changes in the population structure and distribution of species and which indicate long- term variability in their foraging ecology.