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Smale, D. A., Kendrick, G. A., Harvey, E. S., Langlois, T. J., Hovey, R. K., Van Niel, K. P., Waddington, K. I., Bellchambers, L. M., Pember, M. B., Babcock, R. C., Vanderklift, M. A., Thomson, D. P., Jakuba, M. V., Pizarro, O., and Williams, S. B. 2012. Regional-scale benthic monitoring for ecosystem-based fisheries management (EBFM) using an autonomous underwater vehicle (AUV). – ICES Journal of Marine Science, 69: 1108–1118. Monitoring marine habitats and biodiversity is critical for understanding ecological processes, conserving natural resources, and achieving ecosystem-based fisheries management (EBFM). Here, we describe the application of autonomous underwater vehicle (AUV) technology to conduct ongoing monitoring of benthic habitats at two key locations in Western Australia. Benthic assemblages on rocky reefs were sampled with an AUV, which captured >200 000 geo-referenced images. Surveys were designed to obtain 100% coverage of 25 × 25 m patches of benthic habitat. In 2010, multiple patches were surveyed at 15–40-m depths at three reference sites at the Houtman Abrolhos Islands and at six reference sites at Rottnest Island. The following year, repeat surveys of the same geo-referenced patches were conducted. Benthic assemblages at the Houtman Abrolhos Islands were varied in that one reference site was dominated by hard corals, whereas the other two were macroalgae dominated. Conversely, assemblages at Rottnest Island were dominated by the kelp Ecklonia radiata. The AUV resurveyed each patch with high precision and demonstrated adequate power to detect change. Repeated observations at the reference sites will track natural variability in benthic habitat structure, which in turn will facilitate the detection of ecological change and ultimately feed back into EBFM processes.

Metcalf, S. J., Pember, M. B., and Bellchambers, L. M. 2011. Identifying indicators of the effects of fishing using alternative models, uncertainty, and aggregation error. – ICES Journal of Marine Science, 68: 1417–1425. The identification of indicators of the indirect effects of fishing is often an issue for fisheries management, particularly if just commercial catch data are available. Complex, intermediate, and simplified qualitative models were produced for a fishery case study off Western Australia to identify potential indicators of ecosystem change attributable to western rock lobster (Panulirus cygnus) extraction and bait input. Models of intermediate complexity were used to identify indicators because they produced the least aggregation error. Structural uncertainty was considered through a series of structurally different intermediate models. These alternate models consistently predicted that extraction of rock lobster may positively impact small fish of low economic value, such as old wife (Enoplosus armatus), footballer sweep (Neatypus obliquus), and king wrasse (Coris auricularis). These small fish were therefore identified as potential indicators of the effects of rock lobster extraction. Small crustaceans (amphipods and isopods) also displayed positive impacts attributable to bait input from the rock lobster fishery and were identified as potential indicators of bait effects. Monitoring of these indicators may aid the detection of ecosystem change caused by the rock lobster fishery.

Otoliths of king threadfin, Polydactylus macrochir were collected from 2007 to 2009 at nine locations across northern Australia representing most of their distributional range and areas where fisheries are active. Measurement of the stable isotope ratios of δ18O and δ13C in the sagittal otolith carbonate from assemblages of P. macrochir revealed location-specific signatures and indicated that adult fish sampled from representative sites across their range were significantly different. The significant differences in the isotopic signatures of P. macrochir demonstrated that population subdivision is evident and there is unlikely to be substantial movement of fish among these distinct adult assemblages. The stable isotopic signatures for the fish from the different locations were persistent through time, and therefore it could be concluded that they comprise separate stocks for many of the purposes of fisheries management. The spatial separation of these populations indicates a complex stock structure across northern Australia with stocks of P. macrochir associated with large coastal beaches and embayments on a fine spatial scale. These results indicate that in order to achieve optimal fisheries management, the current spatial management arrangements need to be reviewed, particularly the potential for localised depletion of stocks on small spatial scales. This study has provided further evidence that measurement of the stable isotopes ratios in teleost sagittal otolith carbonate can be a valuable tool in the delineation of fishable stocks or fishery management units of adult fish and that widely distributed fish can nonetheless show strong localised population structure.

Ecosystem modelling has predicted that fishing for western rock lobster Panulirus cygnus in deep water (50–80m) habitats will result in increased abundance of their macroinvertebrate prey, which would, in turn, support greater production of small-bodied invertivore fish species. To investigate the potential ecosystem effects of rock lobster fishing, a targeted fisheries closure was proposed in deep water habitats along the coast of Western Australia. Data on small-bodied invertivore fish abundance, from baited video, were used to investigate differences across habitats and simulate the likely power of any study to detect change. In general, small-bodied invertivore fish were more abundant at shallower macroalgae-dominated sites, whereas the most abundant single species, the western king wrasse Coris auricularis, was abundant across all habitats and sites. Power simulation of a mixed-model before–after–control–impact (BACI) design found that a 40–50% decrease in either Coris auricularis or small-bodied invertivore fish in general would be very likely to be detected (power ~0.8). Based on the power simulation, we suggest a general sampling design to investigate change before and after the establishment of the fishery closure and make suggestions for further ecological studies to investigate the predicted ecosystem effects of rock lobster fishing.

Blue swimmer crab (Portunus pelagicus) fisheries in Western Australia have generally been considered robust to recruitment overfishing, as the minimum legal size for retention of these crabs in both the commercial and recreational crab fisheries are set well above the size at sexual maturity allowing crabs to spawn at least once before entering the fishery. However, the Cockburn Sound crab stock suffered a recruit ment collapse, with three key factors: (a) the fishery is near the edge of this species distribution and hence vulnerable to environmental fluctuations; (b) a number of consecutive years of poor environmental conditions resulted in poor recruitments; and (c) high fishing pressure continued on these low recruitments. This study indicates that water temperatures at the start of the spawning season positively influence the strong stock-recruitment relationship for P. pelagicus in Cockburn Sound. Apparently, warm water temperatures at the onset of spawning result in the larger females producing additional broods of eggs, and therefore a far greater number of larvae over the short spawning season. This relationship produces catch predictions for this fishery a year ahead and provides information for the development of biological reference points for management.

Background The western rock lobster, Panulirus cygnus, is endemic to Western Australia and supports substantial commercial and recreational fisheries. Due to and its wide distribution and the commercial and recreational importance of the species a key component of managing western rock lobster is understanding the ecological processes and interactions that may influence lobster abundance and distribution. Using terrain analyses and distribution models of substrate and benthic biota, we assess the physical drivers that influence the distribution of lobsters at a key fishery site. Methods and Findings Using data collected from hydroacoustic and towed video surveys, 20 variables (including geophysical, substrate and biota variables) were developed to predict the distributions of substrate type (three classes of reef, rhodoliths and sand) and dominant biota (kelp, sessile invertebrates and macroalgae) within a 40 km2 area about 30 km off the west Australian coast. Lobster presence/absence data were collected within this area using georeferenced pots. These datasets were used to develop a classification tree model for predicting the distribution of the western rock lobster. Interestingly, kelp and reef were not selected as predictors. Instead, the model selected geophysical and geomorphic scalar variables, which emphasise a mix of terrain within limited distances. The model of lobster presence had an adjusted D2 of 64 and an 80% correct classification. Conclusions Species distribution models indicate that juxtaposition in fine scale terrain is most important to the western rock lobster. While key features like kelp and reef may be important to lobster distribution at a broad scale, it is the fine scale features in terrain that are likely to define its ecological niche. Determining the most appropriate landscape configuration and scale will be essential to refining niche habitats and will aid in selecting appropriate sites for protecting critical lobster habitats.