In order to investigate and monitor the ecological impact of longlines on the benthic environment and subsequently develop strategies for its management, the UK is conducting a series of research projects studying the potential impact of longline fishing gear on benthic habitats. The research has been structured around three approaches, each deploying a different format of benthic camera system and movement sensors. Data collected by the cameras and sensors will be input to models which predict the areas in which benthos is likely to occur and identify potential risks, in order to evaluate their validity and further develop their relevance to advice.
Abstract:
Biomarker analysis, especially fatty acids (FA) and stable isotopes (SI), has become a useful tool to elucidate the flow of energy and trophic interactions in an ecosystem and to analyse the diet of species that are hard to observe while feeding. Herein we compare FA profiles and SI composition (nitrogen, δ15N and carbon, δ13C) of muscle tissue from two sympatric Antarctic fish species - Notothenia rossii and N. coriiceps – that are key components in the inshore ecosystem of the South Shetland Islands. For both nototheniids, potential food sources from the benthic community (algae, amphipods, polychaetes and gastropods) were screened in order to re-evaluate their trophic position (TP) and the energy flow, taking as representative of the area the local food web of Potter Cove, in King George Island/Isla 25 de Mayo. Significant differences in FA and SI composition between the two fish species (δ15N / δ13C N. rossii: 9.94±0.80‰ / -23.64±1.03‰, N. coriiceps: 11.44±0.42‰ / -21.46±0.46‰) were found. Notothenia rossii showed a higher total FA concentration, with high levels of polyunsaturated FA (PUFA) such as EPA, DHA and ARA. Conversely, the potential food sources tested showed low concentrations of these FAs. This could indicate that both nototheniids are feeding mainly on another food source that was not included in the present study, or that FA bioconversion takes place in these species. While the FA results might suggest a possible trophic niche segregation between N. rossii and N. coriiceps, both species occupy a similar TP (N. rossii = 3.1, N. coriiceps = 3.5). Furthermore, we found a higher total concentration of monounsaturated FA (MUFA) in N. rossii (4348.4 μl/µg) than in N. coriiceps (85.6 μl/µg), which is about 50-fold greater, and is related with a higher buoyancy capacity in N. rossii. In the present study the use of trophic biomarkers did not elucidate which was the main prey item as lipid source for N. rossii and N. coriiceps, suggesting that other food sources need to be analysed and the species fatty acid bioconversion capacity should be further investigated.
Abstract:
An observation on the interaction between marine mammal and krill midwater trawl was carried out onboard the Chinese krill fishing vessel Fu Rong Hai during the 2018/19 fishing season. The underwater and on sea surface observations were both deployed. Although large numbers of Antarctic fur seal Arctocephalus gazella were observed around the vessel during the vessel fishing in the Subarea 48.3, no identified marine mammal was observed in the main body of trawl net. There was no marine mammal by-catch observed either. The observation found the Antarctic fur seals would be attracted by the codend of krill trawl net, especially during the periods difficult to get foods. The observation also indirectly implied that well designed seal escaping devices might reduce the risk of accidently by-catch of Antarctic fur seals. Future researches on the interaction between marine mammals and krill fishing gears would be helpful to understand the relationships between krill fishing and krill predators.
There is no abstract available for this document.
There is no abstract available for this document.
There is no abstract available for this document.
Abstract:
We invite Members to collaborate with the U.S. AMLR Program to conduct a multi-national, empirical study of krill flux through the Bransfield Strait and across the continental shelf surrounding Astrolabe Island. We propose to conduct this study with 20+ acoustically instrumented moorings. Collaboration could include refining study design, deploying and recovering moorings, conducting separate acoustic surveys to estimate krill standing stock within the study area, and, ultimately, data analysis and synthesis.