Queensland line fishery (reef) crew-based catch monitoring

Abstract

The Line Fishery (Reef) is Queensland’s second most valuable fishery and operates within the Great Barrier Reef Marine Park (GBRMP), which is a World Heritage Area. A crew-based survey was undertaken with volunteer commercial line fishers self-reporting species composition of their catch (retained, discards and depredation). This project was undertaken to meet Condition 6 of the existing Commonwealth Wildlife Trade Operation (WTO) for the fishery. Condition 6 required measures to be implemented to update existing information on non-retained catch in the fishery. The survey provides new data for the assessment and management of the fishery.
The crew-based surveys included data from five vessels with 19 individual fishers contributing data across 11 trips from Cooktown Region to Swains Region within the GBRMP. Data was collected from three vessels targeting coral trout (Plectropomus spp and Variola spp) and two targeting saddletail snapper (Lutjanus malabaricus) and red emperor (Lutjanus sebae). Catch including retained and released fish from 103 fishing days were reported. A total of 66 fish species or species groups were reported across all catches.
Similarity between contemporary crew-based surveys and historic observer datasets varied among the two fleets. Data showed relatively similar species composition between 2011–12 observer surveys and crew-based surveys for the fishers targeting coral trout with the tropical snapper fishers exhibiting greater differences. Differences in both cases were largely associated with shifts in the relative abundance of dominant target species rather than changes in species occurrence. To extend the analysis, additional data was considered by including historic line survey data extending back to 1996. The longer time frame comparison confirmed the dominant target and byproduct species within the coral trout fishery have remained consistent throughout more than 20 years of data collection.
Crew-based survey estimated 52% of fish were released from vessels targeting coral trout, compared with 35% reported in the 2011–12 observer survey. Catches in the fishery were dominated by target species, most of which were retained. Discarding in the coral trout fishery is likely driven by the diverse species composition and conservative minimum legal size limits for a range of non-target and byproduct species. Discard rates in the tropical snapper fleet were 10.2%, similar to the 8.4% reported from the 2011–12 observer survey.
The impact of depredation was highly variable across fishers and fishing days. Overall depredation rates were higher for the coral trout targeting fishery (3.1%), particularly for the coral trout species group (4.3%) than for species in the tropical snapper fleet (2.1%). However, fewer fishing days were monitored in the tropical snapper fleet. Half of the fishing days were impacted by depredation in the coral trout fleet, while 30% were impacted in the tropical snapper fleet. An average of ~10% to ~12% of the catch was taken when depredation occurred, although some fishers experienced substantially higher rates.
An increased number of Māori wrasse (Cheilinus undulatus) and barramundi cod (Cromileptes altivelis) were caught and released within the coral trout fishery compared to the 2011–12 observer survey. These species have been protected since 2003 and some increased abundance would be expected. There were no interactions with threatened endangered and protected (TEP) species reported. This is consistent with historic research line fishing data.
In summary, this crew-based discard survey project effectively addressed WTO Condition 6 by updating information on catch composition, release practices and depredation in the Queensland Line Fishery (Reef). The survey sampled vessels representative of the major commercial fleets of the fishery, which is predominantly focused on harvest of coral trout. Data collected indicated there had been no substantial shift in catch composition major species contributing to non-retained catch, compared to the 2011–12 observer survey data.
Without cooperation from the commercial fishing industry this data would have been difficult to collect. This project emphasises the critical role of industry engagement in enhancing data collection and fostering ongoing collaboration. These insights provide a foundation for future assessments, ongoing monitoring and management of the fishery.