WAMSI Node 3.2.1 - Diversity, abundance and habitat utilisation of sharks and rays - Offshore / longline survey data

Brief description

Longline fishing was used to survey elasmobranchs outside the reef and was carried out from the Western Australia Fishery Department vessel RV ‘Naturaliste’. A total of 111 longline sets were made between Three Mile Camp towards the southern extremity of the Marine Park, to northeast of the Muiron Islands outside the northern limits of the Park; the distribution of these sets are shown in the thumbnail. Of these 111 sets, 17 were in sanctuary zones and 94 in non-sanctuary zones (in the thumbnail picture the hatched areas are sanctuary zones).

Lineage

Statement: Longline fishing was used to survey elasmobranchs outside the reef and was carried out from the Western Australia Fishery Department vessel RV ‘Naturaliste’. Longlines comprised 1 km of 12 mm diameter mainline with (usually) 50 hooks. Snoods were 8-10 m apart and each snood was 2 m long and had an 11/0 or 12/0 J hook baited with mullet. About 250 hooks were set per day, as between one and five separate lines. Lines were generally set for periods of between 2.4 h and 5.2 h (mean of 3.6 h) over the dawn period but 10 lines (set over 2 days) were set at dusk and retrieved at dawn the following day (mean soak time of 15.2 h). Elasmobranchs that came up alive (the majority) were landed on deck by means of a cradle, identified, measured, sexed, tagged and released. Tags were either Jumbo Rototags inserted in the dorsal fin, or occasionally dart tags inserted in the musculature where tagging was carried out with the fish still in the water. Genetic samples from a representative selection of each species were taken from muscle biopsies or fin clips. Catch per unit effort (cpue) was expressed a number of individuals caught per 100 hooks.

Notes

Credit
JD Stevens, PR Last, WT White (CSIRO Marine & Atmospheric Research, Hobart) RB McAuley (Department of Fisheries, Government of Western Australia, Perth) MG Meekan (Australian Institute of Marine Science, Perth)