Preliminary age-based life history characteristics of the dogtooth tuna, Gymnosarda unicolor (Ruppell, 1838), in the southwest Pacific Ocean

Welch, David J.; Smith, Adam K.; Krusic-Golub, Kyne; Erdmann, Sandra; Newman, Stephen J.

doi:10.1016/j.aaf.2021.12.004

Cited by 1 publication

(1 citation statement)

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“…Shark research has grown in recent decades [ 13 ] and data collected by the public can provide a cost-effective means of monitoring populations of wild animals [ 3 , 14 , 15 ]. Several citizen science initiatives, taking advantage of growing numbers of recreational fishers, Self-Contained Underwater Breathing Apparatus (SCUBA) divers and free divers, have produced information used for conserving and managing fisheries and marine biodiversity [ 16 , 17 , 18 ]. This information includes data on corals, fish and charismatic fauna such as sharks [ 19 , 20 , 21 ].…”

Section: Introductionmentioning

confidence: 99%

Quantifying Catch Rates, Shark Abundance and Depredation Rate at a Spearfishing Competition on the Great Barrier Reef, Australia

Smith

Songcuan

Mitchell

et al. 2022

Biology

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We developed and applied a method to quantify spearfisher effort and catch, shark interactions and shark depredation in a boat-based recreational spearfishing competition in the Great Barrier Reef Marine Park in Queensland. Survey questions were designed to collect targeted quantitative data whilst minimising the survey burden of spearfishers. We provide the first known scientific study of shark depredation during a recreational spearfishing competition and the first scientific study of shark depredation in the Great Barrier Reef region. During the two-day spearfishing competition, nine vessels with a total of 33 spearfishers reported a catch of 144 fish for 115 h of effort (1.25 fish per hour). A subset of the catch comprised nine eligible species under competition rules, of which 47 pelagic fish were weighed. The largest fish captured was a 34.4 kg Sailfish (Istiophorus platypterus). The most common species captured and weighed was Spanish Mackerel (Scomberomorus commerson). The total weight of eligible fish was 332 kg and the average weight of each fish was 7.1 kg. During the two-day event, spearfishers functioned as citizen scientists and counted 358 sharks (115 h effort), averaging 3.11 sharks per hour. Grey Reef Sharks (Carcharhinus amblyrhynchos) comprised 64% of sightings. Nine speared fish were fully depredated by sharks as spearfishers attempted to retrieve their catch, which equates to a depredation rate of 5.9%. The depredated fish included four pelagic fish and five reef fish. The shark species responsible were Grey Reef Shark (C. amblyrhynchos) (66%), Bull Shark (Carcharhinus leucas) (11%), Whitetip Reef Shark (Triaenodon obesus) (11%) and Great Hammerhead (Sphyrna mokarran) (11%). There were spatial differences in fish catch, shark sightings and rates of depredation. We developed a report card that compared average catch of fish, sightings of sharks per hour and depredation rate by survey area, which assists recreational fishers and marine park managers to assess spatio-temporal changes. The participating spearfishers can be regarded as experienced (average 18 days a year for average 13.4 years). Sixty percent of interviewees perceived that shark numbers have increased in the past 10 years, 33% indicated no change and 7% indicated shark numbers had decreased. Total fuel use of all vessels was 2819 L and was equivalent to 6.48 tons of greenhouse gas emissions for the competition.

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