Overlap in distribution and diets of Atlantic mackerel (Scomber scombrus), Norwegian spring-spawning herring (Clupea harengus) and blue whiting (Micromesistius poutassou) in the Norwegian Sea during late summer

Abstract

Based on two large-scale surveys in the Norwegian Sea in July 2004 and 2006 we investigated the potential overlap in distribution and diets and association with environmental variables for mackerel, herring and blue whiting. Mackerel and blue whiting had low overlap in both distribution and diets, and were associated with warm Atlantic and cold prey-rich Arctic waters, respectively. Also, herring and mackerel were negatively correlated, associated with different environmental variables and even had low diet overlap in Atlantic water where the highest overlap in distribution was observed, but these trends were much clearer in 2006 than in 2004. Prey was patchily distributed and data from single stations indicated that feeding was opportunistic, in particular for mackerel. However, mackerel diet width and feeding incidence were similar between the years, whereas herring was more selective in 2004, probably reaching the end of the feeding season. A delayed peak in Calanus availability was indicated in 2006 and may have prolonged the feeding season, partly explain the difference between the years. Our data did not indicate a prey shift due to encounters between mackerel and herring. Concentrated efforts in limited areas are needed to further elucidate this aspect of interaction.

A new compilation of stomach content data for commercially important pelagic fish species in the northeast Atlantic

“…Published sources suggest that the main zooplankton prey organisms in the North Sea are copepods (mainly Calanus finmarchicus) and euphausiids (mainly Meganyctiphanes norvegica), while fish prey include larval sand eel, herring and sprat (Mehl and Westgård, 1983). In the Norwegian Sea published sources suggest that euphausiids, copepods, pteropod molluscs (Limacina retroversa), amphipods, Appendicularia and capelin are the main dietary items (Langøy et al, 2012;Prokopchuk and Sentyabov, 2006). The EURO-BASIN data set confirms these broad patterns (Fig.…”

“…Several authors have suggested that the preferred prey of blue whiting are euphausiids and hyperiid amphipods, although the relative importance of each of these varies depending on season and locality (Prokopchuk and Sentyabov, 2006;Langøy et al, 2012). The EURO-BASIN data set (Tables 1 and 2) shows similar variability in diet composition depending on sampling location (Fig.…”

“…For herring, many detailed diet composition studies of have been published, starting with Hardy (1924) and Jespersen (1928). In the Norwegian Sea diet has been shown to vary depending on availability of food and geographic location (Prokopchuk and Sentyabov, 2006;Langøy et al, 2012). C. finmarchicus is an important prey in summer (about 77 % by weight), but in certain years appendicularians (Oikopleura spp.…”

Environmental change and social conflict: the northeast Atlantic mackerel dispute

“…In 2012, Icelandic scientists reported that the mackerel gains around 43% of their body weight in Icelandic waters which can be expected to have measurable impacts on the ecosystem since the mackerel might outcompete other species for food (Óskarsson et al 2012 Around the same time, research was published that put forward the possibility of the Atlanto-Scandian herring being outcompeted for food by the mackerel within Norwegian waters (Langøy et al 2012). For Norway, this was extremely important knowledge because they hold approximately 60% of the Norwegian Spring-Spawning herring quota.…”

Prey selection of offshore killer whales Orcinus orca in the Northeast Atlantic in late summer: spatial associations with mackerel

“…The water masses were divided into 3 different categories on the basis of the CTD casts: coastal water (warm and steep temperature profile, with salinity at 20 m < 35); Atlantic water (gradually changing temperature profile, with salinity at 20 m ≥35); and Arctic water (cold and steep temperature profile, with salinity at 20 m < 35; see Blindheim 2004, Langøy et al 2012). …”