Quantitative molecular detection of larval Atlantic herring (Clupea harengus) in stomach contents of Atlantic mackerel (Scomber scombrus) marks regions of predation pressure

Abstract

Mortality rates in the early life-history stages of fishes are generally high yet identifying the causes remain unclear. Faltering recruitment rates of Atlantic herring (Clupea harengus) in the Norwegian Sea indicate a need to identify which mortality factors influence larval herring survival. Previous research suggests that increased predation pressure by Atlantic mackerel (Scomber scombrus) may contribute to the disconnect between spawning stock biomass and recruitment. To quantify the contribution of predation pressure by Atlantic mackerel to herring larval mortality, two research cruises were conducted within a probable “hot spot” (67–72° N) for intensified mackerel predation based on particle drift simulations. Mackerel stomach contents were analysed for herring larvae content using droplet digital polymerase chain reaction (ddPCR) with a quantitative molecular detection assay specific for herring. The ddPCR results demonstrate clear predation by mackerel on herring larvae and also suggest that the alternative use of visual examination may give misleading results. Our results show that mackerel should be considered a potentially important predator on herring larvae. The quantitative molecular assay presented here shows great promise as an efficient and specific tool to correctly identify and quantify predation pressure on early life-history stages of fishes.

Highly mixed impacts of near‐future climate change on stock productivity proxies in the North East Atlantic

“…This CIA projected the pelagic complex to respond favourably to warming (Figure 5b), with strengthened northward feeding migration of adult mackerel (Nøttestad et al., 2016) (Appendix S1, Stock Narratives). However, this increased prey field may intensify mackerel predation on Norwegian spring‐spawning herring larvae reducing subsequent recruitment success (Allan et al., 2021).…”

Caught in the middle: bottom-up and top-down processes impacting recruitment in a small pelagic fish

“…Bottomup factors, such as changes in temperature and shifts in the abundance and type of prey, have been proposed as potential drivers of recruitment variability in these populations (Cardinale et al 2009). Other studies have suggested that cannibalism and predation from other forage fishes (e.g., Atlantic mackerel, Scomber scombrus) can have a large impact on larval survival (Allan et al 2021), but the ultimate consequences for recruitment and the relative contribution of each process is still largely unknown (Corten 2013;Skaret et al 2015;Garcia et al 2020). In general, it is now clear that the set of recruitment drivers is highly context-dependent, varying in time and space within and among populations (e.g., Zimmermann et al 2019).…”

Environmental drivers of herring growth and how the perception shifts with time series length

“…The NSS herring population and its environment have undergone drastic changes over the course of the 80 years study period, including the onset of industrial fishing, a population collapse in the late 1960's followed by a full recovery in 1990's, a warming trend over the past decades, and the habitat expansion of the Northeast Atlantic mackerel as a potential competitor and predator of herring eggs and larvae (Skaret et al 2015, Bachiller et al 2016, Allan et al 2021. Considering that growth is the product of an organisms entire life history and the environment it is experiencing (Enberg et al 2012), it is likely that NSS herring has adapted to the changes it has experienced over time.…”