Aggregations and associations in deep-sea chondrichthyans

Abstract

Group living has been recorded across a diverse range of chondrichthyans, but due to a variety of factors, any inferences of social associations in deep-sea cartilaginous fishes have yet to be described. Using a companion preference analysis, aggregating behaviour and associations in deep-sea chondrichthyans (four holocephalans, ten elasmobranchs) were evaluated across class and group size from long-term archived fisheries independent research trawl survey datasets. Results indicated that not all selected species engaged in aggregative behaviour, but those that did suggested patterns of sex- and size-specific associations, which varied with catch density. Adult females were caught most frequently in low densities, and were highly associated with other adult females. Adult males were consistently associated with each other. The nature of associations has important implications for selective mortality by spatial or temporally stratified, or aggregation-targeting, fisheries.

Observations of two deep‐sea chimaeroids in Icelandic waters

“…4-6 C but decreases after that (Stefánsdóttir et al, 2010). Fish spe- (Finucci et al 2018). The data indicate the presence of an apparent male aggregation location, but the data are limited and in general, the causes of sexual segregation in chondrichthyans is still not well understood and is probably complex (Sims, 2005, Finucci et al, 2017, Finucci et al 2018.…”

“…One feature of many elasmobranchs is the tendency to form aggregations or social groupings (Jacoby et al, 2011) and it has been shown that segregation by sex and maturity stage is common in deep-sea chondrichthyans (Cotton & Grubbs, 2015). Information on deep-sea chimaeras, in particular, is scarce but sexual segregation has been shown to occur in several species (Finucci et al 2018). The objective of this study was to compile data from long-term survey time series better to understand the distribution patterns and other biology of these two species.…”

“…Fish spe- (Finucci et al 2018). The data indicate the presence of an apparent male aggregation location, but the data are limited and in general, the causes of sexual segregation in chondrichthyans is still not well understood and is probably complex (Sims, 2005, Finucci et al, 2017, Finucci et al 2018. Spatial segregation by sex is commonly found among sharks; i.e., adult males and females within a species select different habitats for foraging, thermal or social reasons either within the same area or in separate ones (Finucci et Rigby & Simpfendorfer, 2015;Sims, 2005).…”

“…Spatial segregation by sex is commonly found among sharks; i.e., adult males and females within a species select different habitats for foraging, thermal or social reasons either within the same area or in separate ones (Finucci et Rigby & Simpfendorfer, 2015;Sims, 2005). Social factors are believed to play an important role for many chondrichthyan species and it has been proposed to play important role in relation to mating in chimaeras (Finucci et al 2018, Holt et al, 2013. Mating in many elasmobranch species is known to be aggressive (Pratt & Carrier, 2001;Sims, 2005;Whitney et al, 2004).…”

The Life History of the Southern Lanternshark, Etmopterus granulosus, from the Southwestern Indian Ocean

“…Aspects of the life history of this species suggest that mate availability may the limiting factor. A female skewed sex ratio and segregation by both size class and sex (Clerkin, 2017;Finucci, Dunn & Jones, 2018) Etmopterus granulosus, does not exhibit a significant association between female size and litter size. This may be attributed to multiple factors, but could be related to resource availability.…”