Bioenergetics modeling of the annual consumption of zooplankton by pelagic fish feeding in the Northeast Atlantic

Abstract

The present study uses bioenergetics modeling to estimate the annual consumption of the main zooplankton groups by some of the most commercially important planktivorous fish stocks in the Northeast Atlantic, namely Norwegian spring-spawning (NSS) herring (Clupea harengus), blue whiting (Micromesistius poutassou) and NEA mackerel (Scomber scombrus). The data was obtained from scientific surveys in the main feeding area (Norwegian Sea) in the period [2005][2006][2007][2008][2009][2010]. By incorporating novel information about ambient temperature, seasonal growth and changes in the diet from stomach content analyses, annual consumption of the different zooplankton groups by pelagic fish is estimated. The present study estimates higher consumption estimates than previous studies for the three species and suggests that fish might have a greater impact on the zooplankton community as foragers. This way, NEA mackerel, showing the highest daily consumption rates, and NSS herring, annually consume around 10 times their total biomass, whereas blue whiting consume about 6 times their biomass in zooplankton. The three species were estimated to consume an average of 135 million (M) tonnes of zooplankton each year, consisting of 53-85 M tonnes of copepods, 20-32 M tonnes of krill, 8-42 M tonnes of appendicularians and 0.2-1.2 M tonnes of fish, depending on the year. For NSS herring and NEA mackerel the main prey groups are calanoids and appendicularians, showing a peak in consumption during June and June-July, respectively, and suggesting high potential for inter-specific feeding competition between these species. In contrast, blue whiting maintain a low consumption rate from April to September, consuming mainly larger euphausiids. Our results suggest that the three species can coexist regardless of their high abundance, zooplankton consumption rates and overlapping diet. Accordingly, the species might have niche segregation, as they are species specific, showing annual and inter-annual variability in total consumption of the different prey species. These estimates and their inter-annual and interspecific variation are fundamental for understanding fundamental pelagic predator-prey interactions as well as to inform advanced multispecies ecosystem models.PLOS ONE | https://doi.org/10.1371/journal.pone

Geographical expansion of Northeast Atlantic mackerel (Scomber scombrus) in the Nordic Seas from 2007 to 2016 was primarily driven by stock size and constrained by low temperatures

“…At that time DOY effects on cumulative feeding success shifted from positive to negative. This supports Bachiller et al (2018) and Olafsdottir et al (2016) conclusion that mackerel annual feeding season peaks in August. However, in the present study only 3% of stations were collected in the latter half of August and these stations were limited to 2010 and 2011.…”

“…The expansion northward into a thermal habitat below their preferred range (<9°C) may be a trade-off between temperature preferences and prey availability as well as prey quality. The mackerel undertakes this extensive feeding migration during summer to accumulate energy reserves for the subsequent overwintering and spawning season (Olafsdottir et al, 2016, Bachiller et al, 2018. However, the feeding migration does not expand into the Iceland and Greenland Seas (Fig.…”

“…Mackerel prey on a wide size range of prey items (Prokopchuk and Sentyabov, 2006;Langøy et al, 2012;Óskarsson et al, 2016;Bachiller, et al, 2016) of which the larger prey is poorly sampled with WP2-nets (Gjøsaeter et al, 2000). Larger prey items constitute anywhere from none to ~ 85 % of total stomach content (Langøy et al, 2012;Óskarsson et al, 2016;Bachiller et al, 2018). Availability of larger prey is likely to influences cumulative feeding success, but their importance cannot be estimated as the necessary data on abundance of larger prey items is not available.…”

“…It is an opportunistic predator with a wide range of prey species (Langøy et al, 2012;Bachiller et al, 2016). Main prey is calanoid copepods, and to a lesser extent euphausiids, amphipods, other planktonic crustaceans, pelagic molluscs and fish (Prokopchuk and Sentyabov, 2006;Langøy et al, 2012;Óskarsson et al, 2016;Bachiller, et al, 2016Bachiller, et al, , 2018. Observations show that mackerel frequently occupy temperatures ranging from 8°C 6 to 14°C during the summer feeding period (Utne et al, 2012;Nøttestad et al, , 2010Nøttestad et al, -2015Nøttestad et al, , 2016bNøttestad et al, , 2016c.…”

Diet and feeding strategy of Northeast Atlantic mackerel (Scombrus scomber) in Icelandic waters

“…The shift in feeding method can be explained by the energy cost of filter feeding [72] as well as a lower energy density of C . finmarchicus [73]. Thus, mackerel can shift to larger and more energy-rich food sources when available.…”