Fishery effects and benefits of marine protected areas within the Great Barrier Reef Marine Park

Williamson, David (2009) Fishery effects and benefits of marine protected areas within the Great Barrier Reef Marine Park. PhD thesis, James Cook University.

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No-take marine reserves (NTRs) are areas of the marine environment in which fishing and all other extractive activities are prohibited. In many regions of the world, NTRs are now relatively widespread and they are considered to be a fundamental tool in achieving sustainable management of marine habitats, communities and ecosystems. There is a wealth of evidence that networks of adequately protected NTRs can potentially buffer the negative effects of marine resource exploitation, protect or restore natural states of biodiversity and ecosystem function, and deal with many fishery problems that are not effectively addressed by more traditional management measures.

It has been well documented that the abundance, average size, age and per-capita fecundity of fish species which are targeted by fisheries often increase significantly within adequately protected NTRs. It is expected that NTRs may also function to maintain and perhaps enhance fishery yields via recruitment subsidies to fished areas from enhanced populations within NTRs ('recruitment subsidy') and via net-emigration of post-settlement fish from reserves to surrounding fished areas ('spill-over effect'). However, due to the difficulties associated with tracking the dispersal of microscopic pelagic larvae in the marine environment, empirical demonstrations of the potential contribution of NTRs to enhancing fish populations in surrounding areas via recruitment subsidy remain elusive.

This thesis builds on the body of evidence that adequately protected NTRs can generate benefits for exploited species by presenting fishery independent data on the effects of long term NTR protection (12 – 20 years) on fish populations within Australia's iconic Great Barrier Reef Marine Park (GBRMP). Data presented in Chapters 3, 4, and 5 was generated using standard underwater visual census (UVC) methodologies which have been widely used to assess patterns of distribution and abundance in reef fishes and to assess the structure of fish and benthic communities. The research presented here also extends to the development and testing of new tools for tracking fish larval dispersal and defining the demographic connectivity of fish populations. Chapters 6 and 7 of this thesis present the findings of two experiments which assessed the safety and effectiveness of transgenerational isotope labeling (TRAIL) of reef fish larvae using enriched stable isotopes of barium. The final data chapter of this thesis (Chapter 8) provides an overview of research currently underway which is attempting to demonstrate both NTR recruitment subsidies and spill-over effects for target fish species within the GBRMP.

Chapter 3 of this thesis presents quantitative estimates, UVC data, of density and biomass of coral trout (Plectropomus spp.), the major target of the hook and line fisheries on the Great Barrier Reef (GBR), Australia. Data was collected from inshore fringing reefs of the Palm and Whitsunday Island groups, 3-4 years before (1983-1984), and 12-13 years after (1999-2000) the establishment of NTRs in 1987. Density and biomass of coral trout increased significantly (by factors of 5.9 and 6.3 in the Palm Islands and 4.0 and 6.2 in the Whitsunday Islands) in the NTR sites, but not the fished sites, between 1983-1984 and 1999-2000. In 1999-2000, density and biomass of coral trout, and a secondary target of the fisheries, the stripey snapper (Lutjanus carponotatus), were significantly higher in NTR zones than in the fished zones at both island groups. The density and biomass of non-target fish species (Labridae, Siganidae and Chaetodontidae) did not differ significantly between NTR and fished zones at either island group. Results are also presented for a range of other fish species and groups.

Chapter 4 examines the short-term (bi-annual samples over a 3 year period) temporal dynamics of populations of Plectropomus spp., Lutjanus carponotatus, Siganidae and Chaetodontidae within NTR and fished zones of the Palm Island group. Although considerable temporal variation in mean density and biomass was detected for all fish groups, persistent and significant effects of NTR protection were evident for the target fish groups (Plectropomus spp. and L. carponotatus), while as expected, no clear effects of NTR protection were detected for the control (non-target) fish groups (Siganidiae and Chaetodontidae). It was determined that when examining the effects of NTR protection on fish populations, bi-annual UVC sampling of these reefs provided little, if any, benefit over once-yearly sampling. Quantitative estimates of fishing effort near NTRs and rates of zoning infringements (poaching) within the Palm Island group are also provided within chapter 4. It was calculated that the total fishing effort on the fringing reefs surrounding Pelorus Island (fished zone) was approximately 1164 vessels per year, while approximately 91 vessels per year were illegally fishing within the Orpheus Island NTR.

Chapter 5 presents long-term (5 – 9 years) temporal UVC monitoring data for fish populations and the sessile benthic (coral) community on fringing reefs of the Palm, Whitsunday and Keppel Island groups. As in chapter 4, significant temporal variability in mean density and biomass was detected in all fish groups (Plectropomus spp., L. carponotatus, Siganidae, Chaetodontidae) and in the mean cover of live coral. However, the strong effects of NTR protection on target fish species persisted throughout the monitoring period in all three island groups. As previously shown, there were no detectable effects of NTR protection on non-target fish groups or on the benthic community. Data presented in chapters 3, 4 and 5 of this thesis have provided some of the most convincing evidence available that the management zoning of the GBRMP has been effective in protecting target fish species. Enhanced populations of exploited fish species within the NTRs examined here should lead to recruitment subsidy and spill-over benefits for surrounding fished areas. In order to begin examining export effects of NTRs it was necessary to develop and test techniques for tracking larvae of pelagic spawning fish in the marine environment.

Injection of an enriched stable isotope barium chloride (BaCl ₂) solution into female marine fish has been shown to provide an effective chemical marker that is transmitted to developing eggs and is subsequently detectable in the otoliths of larvae and juveniles. The technique provides a new means of mass-marking larval fish and facilitates investigations of larval dispersal patterns, demographic population connectivity and export effects of NTRs. However, successful field applications must be preceded by trials of the technique on target species within controlled conditions.

Chapter 6 of this thesis examines the toxicological and physiological responses of the common coral trout (Plectropomus leopardus), to injection of enriched stable isotope BaCl ₂ solution. Thirty adult P. leopardus were subject to one of two ¹³⁸ BaCl ₂ injection treatment groups (corresponding to dosage rates of 2 mg and 4 mg ¹³⁸ Ba / kg body weight) and a control group in which fish were injected with 0.9% sodium chloride solution. Fish from each group were sampled at post-injection intervals of 48 hours, 1 week, 3 weeks, 5 weeks and 8 weeks, at which time blood and tissue samples were removed from each fish. Residual concentrations of barium and ¹³⁸ Ba: ¹³⁷ Ba ratios were measured in muscle, gonad, liver and bone tissues of each experimental fish. Elevated barium concentrations were detected in all treatment fish tissue samples within 48 hours post-injection. Within muscle tissue, the highest residual barium concentration recorded was 0.29 mg Ba / kg wet weight, 1 week post-injection in the 4 mg ¹³⁸ Ba / kg treatment group. Residual barium concentrations decreased throughout the remainder of the 8 week experimental period in all tissues except bone. The BaCl ₂ injection had no significant effects on measured whole blood parameters or on the plasma concentrations of steroid hormones. It was concluded that enriched barium stable isotopes can be used at low dosages to mark larvae of commercially important marine fish, without adverse effects on the health of the fish or on humans who may consume them.

Chapter 7 provides details of a trial conducted to validate that injection of enriched stable barium isotopes (¹³⁵ Ba and ¹³⁷ Ba) produces unequivocal geochemical tags on the otoliths of offspring of the brown-marbled grouper (Epinephelus fuscoguttatus). The study also assessed potential negative effects on reproductive performance, egg size, condition and larval growth due to injection of adult female fish. The injection of enriched stable barium isotopes at 0.5 mg and 2.0 mg Ba / kg fish weight into the body cavities of gravid females were both 100% successful in the geochemical tagging of the otoliths of larvae from the first spawning after injection. The low dose rate had no negative effects on eggs or larvae. However, the higher dose rate of 2 mg Ba / kg body weight produced small reductions in yolk sac area, oil globule area, standard length and head depth of pre feeding larvae. Given the success of the 0.5 mg / kg dose rate, it is clearly possible to get a reliable mark and keep the concentration below any level that could affect larval growth or survival. The findings presented in chapters 6 and 7 demonstrate that enriched isotope barium injections provide an effective and safe means of mass-marking grouper larvae.

The next development for this project involves the utilisation of our existing monitoring data and these new larval marking technologies to begin examining larval dispersal, connectivity and export effects of NTRs in the field. Although this project is currently still in progress, chapter 8 provides an overview of the outcomes achieved to date. The study was carried out in the Keppel Islands. The specific objectives of the study were to; 1. Utilise the enriched stable isotope marking technique to track larvae of three target fish species (Plectropomus maculatus, Lutjanus carponotatus, Epinephelus quoyanus) from their natal reef of origin within NTRs to their settlement locations; 2. Measure demographic population connectivity, larval dispersal patterns and rates of self- recruitment within a network of marine reserves; 3. Track movements of adult fish within NTRs and from reserves to surrounding fished areas.

Of the recruit fish samples collected in May 2008 and February 2009, only 10 – 20% have currently been analysed for barium isotope markers. One barium tagged P. maculatus recruit (of 63 analysed) and one tagged L. carponotatus recruit (of 35 analysed) have been detected thus far. Of 23 E. quoyanus recruits analysed to date, no barium tagged individuals have been detected. Both of the tagged recruits obtained thus far were recaptured on reefs which are in very close proximity (less than 2km) to the natal reef on which they were spawned. The tagged P. maculatus recruit dispersed from its natal NTR reef and settled into an adjoining fished zone reef. The tagged L. carponotatus recruit was retained (self-recruited) within its natal NTR reef. The number of barium tagged recruits is likely to increase as further otolith samples are analysed, at which stage, an in depth analysis of dispersal patterns will be conducted.

To date, 12 adult E. quoyanus and 3 L. carponotatus have been recaptured in close proximity to the marine reserve boundary which runs between the western end of Clam Bay and the northern end of Halfway Island, Keppel Island group. In these 15 cases, the total distance moved from tagging to recapture location is less than 1 km. Three P. maculatus have also been captured outside of marine reserve boundaries. Two of these fish moved a distance of approximately 2 km, from within the Clam Bay NTR, to areas outside the reserve. One individual P. maculatus which was tagged at the Middle Island reserve (23°10.066´ S, 150°55. 042´ E) in January 2008 was recaptured at Middle Rock (23°59.799´ S, 151°46.531´ E) in November 2008. This fish was 430 mm in total length, and the movement undertaken represents a straight line distance of approximately 125 km.

Although the results of the study reported in Chapter 8 are currently incomplete, a significant amount of valuable information has already been obtained. Of fundamental importance, is the demonstration that the trans-generational larval marking technique which was trial[l]ed and reported in chapters 6 and 7 of this thesis, can be successfully applied to large, pelagic spawning reef fish species in the field.

The findings presented in this thesis have provided a significant contribution to the understanding of the effects of NTRs on fish populations within the GBR Marine Park. It is my hope that utility will be found in the data presented here and that it can be treated as a robust baseline for continued monitoring of fish and benthic communities on these inshore fringing reefs. Furthermore, I encourage researchers to continue to push the boundaries of what has traditionally been seen as possible, form multi-skilled collaborative teams and tackle the formidable issues currently facing coral reefs and other marine ecosystems.

Item ID: 9677
Item Type: Thesis (PhD)
Keywords: fish populations; fish stocks; fisheries; fishery management tools; fishing industry; GBR; GBRMP; GBRWHA; Great Barrier Reef Marine Park; Great Barrier Reef World Heritage Area; marine conservation zones; marine protected areas; marine reserves; MCZs; MPAs; North Queensland; Northern Australia; no-take zones; NTZs; sustainable fisheries
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Publications arising from this thesis are available from the Related URLs field. The publications are:

Williamson, D.H., Russ, G.R., and Ayling, A.M. (2004) No-take marine reserves increase abundance and biomass of reef fish on inshore fringing reefs of the Great Barrier Reef. Environmental Conservation, 31 (2). pp. 149-159.

Williamson, David, Jones, Geoffrey, Thorrold, Simon R, and Frisch, Ashley J. (2009) Transgenerational marking of marine fish larvae: stable-isotope retention, physiological effects and health issues. Journal of Fish Biology, 74 (4). pp. 891-905.

Williamson, David H., Jones, Geoffrey P., and Thorrold, Simon R. (2009) An experimental evaluation of transgenerational isotope labelling in a coral reef grouper. Marine Biology, 156 . pp. 2517-2525.

Chin, Andrew, Sweatman, Hugh, Forbes, Susan, Perks, Helen, Walker, Ryan, Jones, Geoff, Williamson, David, Evans, Richard, Hartley, Fraser, Armstrong, Shannon, Malcolm, Hamish, and Edgar, Graham (2008) 2008 Status of the coral reefs in Australia and Papua New Guinea. In: Status of Coral Reefs of the World: 2008. Global Coral Reef Monitoring Network, Townsville, QLD, Australia, pp. 159-176.

Davis, K.L.F., Russ, G.R., Williamson, D.H., and Evans, R.D. (2004) Surveillance and poaching on inshore reefs of the Great Barrier Reef Marine Park. Coastal Management, 32 (4). pp. 373-387.

Diaz-Pulido, Guillermo, McCook, Laurence, Dove, Sophie, Berkelmans, Ray, Roff, George, Kline, David I., Weeks, Scarla, Evans, Richard D., Williamson, David H., and Hoegh-Guldberg, Ove (2009) Doom and boom on a resilient reef: climate change, algal overgrowth and coral recovery. PLoS ONE, 4 (4).

Russ, Garry R., Cheal, Alistair J., Dolman, Andrew M., Emslie, Michael J., Evans, Richard D., Miller, Ian, Sweatman, Hugh, and Williamson, David H. (2008) Rapid increase in fish numbers follows creation of world's largest marine reserve network. Current Biology, 18 (12). pp. 514-515.

Date Deposited: 17 Jan 2013 06:18
FoR Codes: 05 ENVIRONMENTAL SCIENCES > 0502 Environmental Science and Management > 050202 Conservation and Biodiversity @ 25%
05 ENVIRONMENTAL SCIENCES > 0502 Environmental Science and Management > 050206 Environmental Monitoring @ 25%
06 BIOLOGICAL SCIENCES > 0602 Ecology > 060205 Marine and Estuarine Ecology (incl Marine Ichthyology) @ 50%
SEO Codes: 96 ENVIRONMENT > 9605 Ecosystem Assessment and Management > 960506 Ecosystem Assessment and Management of Fresh, Ground and Surface Water Environments @ 90%
96 ENVIRONMENT > 9603 Climate and Climate Change > 960305 Ecosystem Adaptation to Climate Change @ 10%
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