Feeding Ecology of Northeast Atlantic Mackerel, Norwegian Spring-Spawning Herring and Blue Whiting in the Norwegian Sea

Abstract

The Norwegian spring-spawning (NSS) herring (Clupea harengus), blue whiting (Micromesistius poutassou) and Northeast Atlantic (NEA) mackerel (Scomber scombrus) are extremely abundant pelagic planktivores that feed in the Norwegian Sea (NS) during spring and summer. This study investigated the feeding ecology and diet composition of these commercially important fish stocks on the basis of biological data, including an extensive set of stomach samples in combination with hydrographical data, zooplankton samples and acoustic abundance data from 12 stock monitoring surveys carried out in 2005–2010. Mackerel were absent during the spring, but had generally high feeding overlap with herring in the summer, with a diet mainly based on calanoid copepods, especially Calanus finmarchicus, as well as a similar diet width. Stomach fullness in herring diminished from spring to summer and feeding incidence was lower than that of mackerel in summer. However, stomach fullness did not differ between the two species, indicating that herring maintain an equally efficient pattern of feeding as mackerel in summer, but on a diet that is less dominated by copepods and is more reliant on larger prey. Blue whiting tended to have a low dietary overlap with mackerel and herring, with larger prey such as euphausiids and amphipods dominating, and stomach fullness and feeding incidence increasing with length. For all the species, feeding incidence increased with decreasing temperature, and for mackerel so did stomach fullness, indicating that feeding activity is highest in areas associated with colder water masses. Significant annual effects on diet composition and feeding-related variables suggested that the three species are able to adapt to different food and environmental conditions. These annual effects are likely to have an important impact on the predation pressure on different plankton groups and the carrying capacity of individual systems, and emphasise the importance of regular monitoring of pelagic fish diets.

Diets and trophic niches of the main commercial fish species from the Celtic Sea

“…Micromeistius poutassou is a planktivore, eating crustaceans, particularly euphausiids (krill), copepods, amphipods (especially hyperiids) and carideans (e.g. Pasiphaeidae species) (Sorbe, 1980;Cabral & Murta, 2002;Prokopchuk & Sentyabov, 2006;Andrey et al, 2010;Bachiller et al, 2016). A high consumption of krill has been observed in almost all of these previous studies.…”

Long‐term variability in overwintering copepod populations in the Lofoten Basin: The role of the North Atlantic oscillation and trophic effects

“…One well‐studied species is the copepod Calanus finmarchicus (Gunnerus, 1770), which frequently contributes > 50% to total mesozooplankton biomass in the North Atlantic and subarctic Nordic Seas (Planque and Batten ; Carstensen et al ). It is the main prey item for a wide range of predators, including predatory copepods, medusae, krill, chaetognaths, herring, mackerel, blue whiting, mesopelagic fish, and right whales (Baumgartner et al ; Falk‐Petersen et al ; Bachiller et al ). In recent years, humans also started exploiting the species in the Norwegian Sea, where copepods are harvested to obtain oil‐derived products for dietary use (Vang ).…”

Oogenesis and reproductive investment of Atlantic herring are functions of not only present but long-ago environmental influences as well

“…This view was encouraged by that the predictive power (R 2 ) of F P weakened with advancement in OD from 300 to 500 μm (SI Appendix, Table S4, July), seen also partly from 900 to 1,200 μm (SI Appendix, Table S3, February). However, R 2 in July was generally low, probably due to rapidly changing body metrics at this time of peak feeding (15). In summary, P&GSF and GSF showed highly different size-specific F P and RF P,W trajectories as a function of K, although collectively responding positively to increasing K (SI Appendix, Fig.…”

“…No earlier reproductive information existed for NASH (27), comparably much smaller in stock size (28). As typical for these size-specific visual or filter feeders (15), gonad growth is fueled by preying on zooplankton in the upper water layers until overwintering (21,22). Note that both North Sea herring (winter and autumn spawners combined) and NSSH collapsed in the late 1960s but recovered after management regulations (SI Appendix, Fig.…”

“…The sustainable harvest and well-being of this major player in the North Atlantic has recently been debated within the framework of the carrying capacity of pelagic ecosystems, with special reference to the Norwegian Sea due to the northerly shift in the migration of Atlantic mackerel (Scomber scombrus) (SI Appendix, Fig. S2) (15). Major, transient falls in the abundance of prey (zooplankton) have been noted, but also seen before "the present mackerel era" (SI Appendix, Figs.…”