Some observations on the biology of two rarely seen deep‐sea chimaerids, Chimaera carophila and Hydrolagus homonycteris

Abstract

Chimaera carophila (n = 45) and Hydrolagus homonycteris (n = 11), two deep-sea chimaerids rarely caught in the waters off New Zealand, were collected from research trawl catches and commercial fishery catches around New Zealand at depths between 400 and 1300 m, between 2014 and 2016. Additional preserved specimens of both species (n = 58) from museum collections were analysed for size, sex and maturity. External assessment of male claspers and a combination of internal assessments of female gonad mass and oviducal gland width, were used to determine maturity. For both species, length at first maturity was 0·70-0·82 of their maximum observed chimaera length (L ), with females maturing at a larger size. Length at maturity for C. carophila (L range: 28·7-103·9 cm) was estimated at 72·5 cm L for males (n = 163) and 82·5 L for females (n = 58). In H. homonycteris, length at maturity (length range: 78·6-99·8 cm L ) was estimated at 79·1 cm L for males (n = 51) and 80·1 cm L for females (n = 17). Ovarian fecundity was up to 31 for C. carophila and sperm storage was confirmed in the oviducal gland of this species. Both species preyed on benthic invertebrates. Some C. carophila and H. homonycteris inhabit depths beyond most current fisheries, but both species appear to be relatively rare and have reproductive parameters characteristic of low productivity, which may make these species vulnerable to population decline if mortality was to increase in the future.

Vacchi's palatal organ: a widespread trait in Holocephali

“…The consistency in toothplate and VO morphology observed across the genera Chimaera , Hydrolagus , and Harriotta is complemented by previous studies that have described comparable diet patterns across these groups (Dunn et al, ; Jones, ; Finucci et al, ). Diets of these species consist predominately of crustaceans, sea urchins, molluscs, and polychaetes, which would require grinder toothplates for mastication (Huber et al, ).…”

Ghosts of the deep – Biodiversity, fisheries, and extinction risk of ghost sharks

“…Life‐history studies on deepwater species in particular have been limited to a handful of species commonly caught as by‐catch in regional fisheries (e.g. Barnett et al., 2009; Finucci et al., 2017; Finucci et al., 2017). These studies have indicated ghost sharks are likely more productive than other chondrichthyans, for example Chimaera monstrosa has been shown to have a high intrinsic rebound potential relative to other deepwater chondrichthyans (Kyne & Simpfendorfer, 2007).…”

The Paleozoic assembly of the holocephalian body plan far preceded post-Cretaceous radiations into the ocean depths

“…Holocephalian diversity is currently concentrated in oceanic environments below depths of 200 meters [17][18][19][20][21]. Given their ancient common ancestry with other vertebrates, deepwater chimaeras and ghost sharks lend credence to the hypothesis that mesopelagic and bathypelagic environments have served as a refuge for ancient biodiversity that has become rare or extinct in other ecosystems [22,23].…”