Abstract
The deepwater chondrichthyan fauna of the Great Barrier Reef is poorly known and life history information is required to enable their effective management as they are inherently vulnerable to exploitation. The chondrichthyan bycatch from the deepwater eastern king prawn fishery at the Swain Reefs in the southern Great Barrier Reef was examined to determine the species present and provide information on their life histories. In all, 1533 individuals were collected from 11 deepwater chondrichthyan species, with the Argus skate Dipturus polyommata, piked spurdog Squalus megalops and pale spotted catshark Asymbolus pallidus the most commonly caught. All but one species is endemic to Australia with five species restricted to waters offshore from Queensland. The extent of life history information available for each species varied but the life history traits across all species were characteristic of deep water chondrichthyans with relatively large length at maturity, small litters and low ovarian fecundity; all indicative of low biological productivity. However, variability among these traits and spatial and bathymetric distributions of the species suggests differing degrees of resilience to fishing pressure. To ensure the sustainability of these bycatch species, monitoring of their catches in the deepwater eastern king prawn fishery is recommended.
Highlights
Deepwater chondrichthyans are generally slower growing, later maturing and longer lived than chondrichthyans from shelf and pelagic habitats [1]
This study increased the known number of deepwater chondrichthyan species recorded from the deepwater eastern king prawn (EKP) fishery around the Swain Reefs
The D. polyommata traits were mostly typical of small-medium bodies skates as it had a moderately fast growth rate, which was faster than that of the two shark species, and it had a shorter life span and younger age at maturity than the two shark species [27, 28]
Summary
Deepwater chondrichthyans (i.e. shark, skate, ray and chimaera species whose distributions or majority of life cycle is predominantly below 200 m depth) are generally slower growing, later maturing and longer lived than chondrichthyans from shelf and pelagic habitats [1]. This reduces their biological productivity and capacity to recover from exploitation, rendering them typically more vulnerable to fishing pressure than chondrichthyans from other habitats [2, 3]. Information on the life history of many deepwater chondrichthyan species is lacking and is needed to enable assessment of their ability to sustain fishing pressure and for the development of effective conservation and management strategies [4].
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