Spatio-temporal variability in the demersal fish assemblage on the outer continental shelf of the Great Australian Bight

Nitschke, Joshua; Knuckey, Ian; Koopman, Matt; Hudson, Russell; Huveneers, Charlie; Grammer, Gretchen L.; Ward, Tim M.

doi:10.1016/j.ecss.2022.107852

Cited by 3 publications

(1 citation statement)

References 84 publications

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“…Reduction in the prey resources AUFS depend upon are likely due to ecosystem changes. Indeed, there has been sustained low biomass levels of several commercial fish species which have not recovered despite reduced fishing pressure (Edgar et al, 2018;Nitschke et al, 2022), suggesting wider ecosystem changes have occurred. While the exact linkages between environmental variables and prey diversity, abundance and distribution for the species are not known (Kirkwood et al, 2008;Kliska, 2016;Kliska et al, 2022), the results of the present study demonstrate local-and broad-scale influences on AUFS body condition over the last two decades.…”

Section: Body Condition Decrease: Potential Causes and Implicationsmentioning

confidence: 99%

Long-term decline in body condition of female Australian fur seals: potential causes and implications

Geeson,

Hindell,

Hobday

et al. 2023

Front. Mar. Sci.

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The Australian fur seal (Arctocephalus pusillus doriferus, AUFS) population is still recovering from the over-exploitation of the commercial-sealing era (18th and 19th centuries). While the population is considered to be only < 47% of its pre-harvest size, it now represents the greatest resident marine predator biomass in the south-eastern Australian marine ecosystem. The region is experiencing rapid environmental change and, as a keystone predator species, the AUFS is an indicator of ecosystem health. In the present study, the body mass, standard length and body condition index (BCI) were analysed between 1997-2021 in adult female AUFS provisioning pups on Kanowna Island (northern Bass Strait), the third largest colony for the species. While substantial inter-annual fluctuations were observed, there was no temporal trend in standard length during the 23-year study period. In contrast, body mass and, consequently, BCI decreased significantly, suggesting the population is experiencing changing nutritional conditions. While these changes do not appear to be due to competition with commercial fisheries or population expansion, weak but significant negative relationships were observed between BCI and 1-year lagged sea surface temperature and summer zonal winds in the Bonney Upwelling region, and both current- and 2-year lagged Indian Ocean Dipole (IOD). These findings suggest the BCI of AUFS may continue to decline under predicted climate change conditions. While a lack of a concurrent decline in pup production could indicate a degree of nutritional tolerance or flexibility in energy allocation, further monitoring is required to assess decreases in reproductive parameters (e.g., birth mass, pre-weaning growth rates) or vital rates, which would be expected with continued nutritional stress.

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Section: Body Condition Decrease: Potential Causes and Implicationsmentioning

confidence: 99%

Long-term decline in body condition of female Australian fur seals: potential causes and implications

Geeson,

Hindell,

Hobday

et al. 2023

Front. Mar. Sci.

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Complementary Non‐invasive Fish Monitoring Distinguishes Depth‐Dependent Fish Communities

Burns,

Mallawaarachchi,

Clarke

et al. 2024

Environmental DNA

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Human activities are increasingly affecting marine environments, with fish communities serving as critical indicators of ecosystem health. Effective management of marine fishes is imperative for maintaining the balance of marine ecosystems, necessitating comprehensive monitoring strategies. We used baited remote underwater video systems (BRUVS) and environmental DNA (eDNA) survey methods to assess fish communities across four offshore islands and seamount groups in Australia's eastern Great Australian Bight (GAB). Employing a paired sampling design, we conducted 32 BRUVS deployments and collected 32 eDNA samples in tandem. We compared the taxonomic and functional diversity of fish detected by these two methods and explored fish assemblage within the eastern GAB. Our findings demonstrated that BRUVS and eDNA data were complementary to each other, with each approach detecting distinct segments of the fish community. Only 17 of the 102 species recorded were detected by both methods and combining these two datasets resulted in a 40% increase in species‐level detections compared to either method alone. BRUVS predominantly identified benthic and demersal fish, whereas eDNA predominately identified pelagic species, including species of conservation (e.g., white sharks) and commercial significance (e.g., southern bluefin tuna). Yet, both methods distinguished depth‐dependent communities within a single sampling site. These findings emphasize the value of integrating multiple approaches for enhanced fish species detection, offering valuable insights into future biodiversity monitoring and conservation efforts.

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Difference in seasonal shift of spatial homogenization between taxonomic and functional structure in demersal fish communities

Li,

Ma,

et al. 2023

Estuarine, Coastal and Shelf Science

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Spatio-temporal variability in the demersal fish assemblage on the outer continental shelf of the Great Australian Bight

Cited by 3 publications

References 84 publications

Long-term decline in body condition of female Australian fur seals: potential causes and implications

Long-term decline in body condition of female Australian fur seals: potential causes and implications

Complementary Non‐invasive Fish Monitoring Distinguishes Depth‐Dependent Fish Communities

Difference in seasonal shift of spatial homogenization between taxonomic and functional structure in demersal fish communities

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