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Coffs Harbour, Australia

Gray C.A.,WildFish Research | Gray C.A.,Sydney Institute of Marine Science | Johnson D.D.,National Marine Science Center | Reynolds D.,Northern Fisheries Center | Rotherham D.,Text Laboratory
Fisheries Research | Year: 2014

We assessed a time-based technique for estimating the relative abundance and size composition of populations of the beach clam, Donax deltoides, in the swash zone of exposed ocean beaches by comparing it with a standard quadrat-based method. The time-based method consisted digging small plots of sand by hand and scooping sediment and clams into a mesh bag attached to a rigid frame. We tested three digging times (30, 60 and 120. s) and two mesh sizes (12 and 19. mm). Compared to a standard box-quadrat, the time-based diggings were more effective and efficient in terms of numbers of clams collected per time taken to do a sample. The timed digging technique was also much simpler and less problematic to use in the swash zone, which is important when industry are involved in sampling. Although a greater total number of clams were collected in the 120. s diggings, when the CPUE data were standardized to number per 30. s, a greater proportion of clams were collected in the shortest time frame tested. This suggests most clams were captured in the first 30. s of digging, with fewer caught per unit of time thereafter. A major benefit of using the shortest digging time is that a greater number of replicate samples and patches of clams on a beach can be sampled per given unit of time, potentially improving overall precision without large increases in costs. An optimal sampling design would involve sampling more patches on a beach than replicates within a patch. Given a sampling window of 3. h either side of low tide, we suggest that future sampling should incorporate 6 replicate 30-s diggings at each of 8 patches on a beach. We further recommend that a 12. mm mesh bag be used as it retained a greater proportion of small clams (<20. mm). This study highlights the importance of doing pilot studies to develop appropriate sampling gears and for determining optimal, cost-effective sampling strategies for large-scale surveys. © 2014 Elsevier B.V. Source

Adjeroud M.,Institute Of Recherche Pour Le Developpement | Adjeroud M.,CNRS Host-Pathogen-Environment Interactions Laboratory | Fernandez J.M.,Center Ird Of Noumea | Fernandez J.M.,CEA Cadarache Center | And 6 more authors.
Marine Pollution Bulletin | Year: 2010

We investigated the spatial distribution of adult and juvenile coral assemblages in the southwestern lagoon of New Caledonia, from disturbed fringing reefs within bays, to oceanic barrier reefs. Generic richness, abundance, and percent cover were highly variable at this scale, but no clear cross-shelf gradient was found. Rather, community composition was more related to reef biotopes. Correlations and canonical correspondence analyses revealed that composition and abundance of coral assemblages were related to substrate types (cover of turf algae and cover of encrusting coralline algae), but not to water quality or metal concentrations in sediments. We found a strong relationship between juvenile and adult distribution for all dominant genera, which suggests that recruitment processes are also a major factor structuring these populations. The densities of juveniles and their proportion in the coral assemblages were relatively low, which implies that replenishment capacities and potential for recovery are probably limited for these reefs. © 2010 Elsevier Ltd. Source

Scott A.,National Marine Science Center | Scott A.,Southern Cross University of Australia | Malcolm H.A.,Solitary Islands Marine Park | Damiano C.,National Marine Science Center | And 2 more authors.
Marine and Freshwater Research | Year: 2011

Understanding the population dynamics of host sea anemones and their symbiotic anemonefish is important given that pressures such as aquarium collecting and bleaching events are adversely impacting their abundance in some IndoPacific locations. We examined long-term trends in anemone and anemonefish abundance at four sites within a 'no-take' zone at North Solitary Island, Australia, by comparing data from 2008 to surveys done in 1994 and 1995. Species richness was stable, comprising two anemones, Entacmaea quadricolor and Heteractis crispa, and three anemonefishes, Amphiprion akindynos, A. latezonatus, and A. melanopus. In 2008, densities of the most abundant species, E. quadricolor and A. akindynos, were substantially higher than previously recorded, with increases of up to 532% and 133%, respectively. There was a strong relationship between A. akindynos densities and anemone cover, whereas A. latezonatus had higher densities in deeper waters. Densities of this species remained similar over time, although there was a decline at one site. Heteractis crispa and A. melanopus were found in comparatively low numbers. Potential reasons for the overall increase in abundance include: protection from severe swell events, the lack of major bleaching events, the ability of E. quadricolor to reproduce rapidly by asexual reproduction, and the increasing duration of marine park protection. © CSIRO 2011. Source

Gilbert J.M.,Southern Cross University of Australia | Baduel C.,University of Queensland | Li Y.,University of Queensland | Reichelt-Brushett A.J.,Southern Cross University of Australia | And 7 more authors.
Marine Pollution Bulletin | Year: 2015

Polychlorinated biphenyls (PCBs) are ubiquitous pollutants in the marine environment that are known to accumulate in apex predators such as sharks. Liver samples from dusky Carcharhinus obscurus, sandbar Carcharhinus plumbeus, and white Carcharodon carcharias sharks from south-eastern Australian waters were analysed for the seven indicator PCBs 28, 52, 101, 118, 138, 153 and 180. Median ∑PCBs were significantly higher in white than sandbar sharks (3.35 and 0.36μgg-1 lipid, respectively, p=0.05) but there were no significant differences between dusky sharks (1.31μgg-1 lipid) and the other two species. Congener concentrations were also significantly higher in white sharks. Significant differences in PCB concentrations between mature and immature dusky (3.78 and 0.76μgg-1 lipid, respectively) and sandbar (1.94 and 0.18μgg-1 lipid, respectively) sharks indicated that PCB concentrations in these species increased with age/growth. Higher-chlorinated congeners (hexa and heptachlorobiphenyls) dominated results, accounting for ~90% of ∑PCBs. © 2015. Source

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