Fisheries Long Term Monitoring Program
- C Lunow, S Helmke, C Bullock
- Publication details:
- Department of Primary Industries, Brisbane, Australia
- August 2003
- Bibliographic details:
- 71 pages
Queensland's coral reef line fishery was worth around $38-40 million to commercial fishers in 2001 and comprised fish harvested throughout the Great Barrier Reef area from the Torres Strait (10.5° S) to Baffle Creek (24.5º S). Queensland Fisheries is responsible for managing and monitoring the status of this fishery. In 1999 a fishery-independent survey of reef fish stocks was started to complement information collected on this fishery through the commercial log-books and the recreational fishing surveys. As part of the Long Term Monitoring Program (LTMP), these surveys estimate relative population abundance and size frequency of the primary target species, coral trout. Using underwater visual census (UVC) techniques data can be collected on a variety of reef fish species while surveying coral trout.
The LTMP collects visual census data each year from 20 reefs between Lizard Island and the Whitsundays. Reefs were selected because they had historical UVC estimates of the target species from previous research and monitoring projects. Data collected by the LTMP includes the number and size of target fish species and benthic habitat data. This data allows an assessment of relative population abundances, biomass estimates and population structure. Species included in the survey are the common coral trout (Plectropomus leopardus), blue-spot coral trout (Plectropomus laevis), barred-cheek coral trout (Plectropomus maculatus), passionfruit coral trout (Plectropomus areolatus), high-fin coral trout (Plectropomus oligocanthus), red throat emperor (Lethrinus miniatus), spangled emperor (Lethrinus nebulosa), red bass (Lutjanus bohar), stripey (Lutjanus carponotatus), Moses perch (Lutjanus russelli), Maori wrasse (Cheilinus undulatus) and barramundi cod (Cromileptes altivelis).
Preliminary results of the LTMP reef fish surveys are presented in this report. Results are from three years of survey data (1999 to 2001) and highlight some important aspects of these populations. While the relative density of most target species is variable between years, declining trends have been recorded for common coral trout, red bass and Moses perch. The mean size of observed common coral trout has declined from 34.3 cm in the first survey in 1999 to 32.9 cm in 2001. While not statistically significant, this may be a warning of growth overfishing of this species and should be more closely investigated. Barramundi cod and stripey have also displayed a decreasing trend in average size across survey years, although these trends were also not statistically significant. Care needs to be taken in interpreting these preliminary results, as the UVC survey design may not have adequate power to detect such small changes in the species being recorded. A future report will include the results of a power analysis for each species.
Regional patterns in abundance and size indicate that Maori wrasse, red throat emperor, stripey and common coral trout were most common, and that red bass and stripey tended to be larger on southern reefs. Spangled emperor tended to be more common on northern reefs than on southern reefs. The outer reefs off Townsville, protected by Marine Park fishing closures, tended to support higher densities of blue-spot coral trout. Of concern is the trend of decreasing density of common coral trout, blue spot coral trout, stripey and barramundi cod in the southern region for both 2000 and 2001 compared to 1999.
Preliminary analysis of data collected on benthic habitat for each transect surveyed did not produce any correlative results with fish abundance.
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