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Incidental catch of marine organisms registered in the Chilean Antarctic krill fishery, years 2012-2016
Abstract and Figures
Krill (Euphausia superba) catch is currently the most relevant fishery industry in Antarctic waters. This resource is a keystone species in the Antarctic food web, sustaining the contribution to the trophic ecology of many invertebrate and vertebrate species. To catch krill, part of the fleet in this fishery uses large mid-water nets that also retain a diversity of other organisms like plankton, meroplankton, and fish species as bycatch. Therefore, it is necessary to understand and evaluate the magnitude of this incidental catch, as well as the potential interactions between krill fishing gear with seabirds and mammals. To estimate the composition and extent of bycatch for this fishery included 784 samples of 25 kg and an equal number of 1 kg sub-samples obtained from Antarctic krill catches in Subarea 48, between years 2012 and 2016. A total of 15 fish species were identified along with the record of five other taxa and other unidentified specimens. The most relevant fish species bycaught by weight were mackerel icefish Champsocephalus gunnari, South Georgia icefish Pseudochaenichthys georgianus, and painted notie Lepidonotothen larseni. Additionally, 20 interactions with seabirds and nine interactions with Antarctic fur seals (Arctocephalus gazella) were registered. In the five years of operations, only three seabirds died, and only two individuals of A. gazelle caught by the net were killed.
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... For the 2018/19 season, fishing for toothfish and other fin-fish was still prohibited in subarea 48.1 with exceptions for research purposes (CCAMLR, 2018). Subarea 48.1 at time of writing was mainly used for krill (Euphausiacea) fisheries via midwater trawling, where macrourids are not common by-catch (Watters, 1996;Arana and Rolleri, 2020). Although, the three carcasses are unlikely to originate from krill fishery by-catch, it is possible that they resulted from fisheries, in particular since fishing vessels were present close to the study location on the day the carcasses were found (Figure 1). ...
When pelagic organisms die and fall onto the deep-sea floor they create food falls, i.e., parcels of organic enrichment that subsidize deep benthic scavenging communities. The diversity and quantities of food falls remain unstudied for many ocean regions since they are stochastically deposited and rapidly scavenged. The Southern Ocean habitat supports large populations of megafauna but few food falls have been documented. To investigate the diversity and quantity of food falls in the northwestern Weddell Sea, we analyzed 8476 images from the deep seafloor that were captured during the expedition PS118 on RV Polarstern in 2019 by the camera system OFOBS (Ocean Floor Observation and Bathymetry System). OFOBS was towed 1.5 m above the seafloor along five transects (400 to 2200 m seafloor depth) east of the Antarctic Peninsula. We observed the carcasses of one baleen whale, one penguin, and four fish at depths of 647 m, 613 m, 647 m, 2136 m, 2165 m, and 2112 m, respectively, as well as associated scavenging fauna. To the best of our knowledge, we describe here the first in situ observations of deep-sea food falls for penguins and fish in the Southern Ocean. While the whale carcass seemed in an intermediate successional stage, both the penguin and the fish were likely recently deposited and three of the fish potentially resulted from fishery discards. Our relatively small data set suggests that a diverse array of food falls provide nutrients to the slopes of the Powell Basin.
The Antarctic Peninsula ecosystem is extremely sensitive to climatic variability and other anthropogenic perturbances ascribed to biomass extraction by fisheries. An Ecopath with Ecosim model calibrated for the 1996-2012 period was projected into the future (2100) under three different climate projections for environmental variables (sea ice extent, open water area and chlorophyll-a concentration) and three Antarctic krill fishery scenarios (no-take, constant and decadal increase until doubling of the current catches). The relative impact of different drivers controlling Antarctic food web dynamics was evaluated with a sensitivity analysis and the temporal variability of several functional group and ecosystem indicators. Under these scenarios, environmental variability resulted in a greater impact on the Antarctic food web in 2100 projections compared with the krill fishery. Chlorophyll-a biomass strongly influenced the temporal variability of functional groups, suggesting predominant bottom-up control on the food web. An alternative food web structure was observed in 2100, with a marked decline in krill population biomass (from less than 50% to near extinction depending on the environmental projection) and an increase in salps and other zooplankton groups. A reduction in the biomass of sea ice and krill-dependent predators, such as Adélie and chinstrap penguins and crabeater seals, was also observed. The absence of functions modelling the spatial and seasonal variability of the krill fishery might cause an underestimation of its ecosystem impacts. This work provides useful insights into the dynamic responses of the Antarctic food web under likely environmental projections and highlights critical points that need to be addressed to improve the understanding and parametrization of the Antarctic food web to anticipate future variability.
Antarctic krill (Euphausia superba) is a key resource in the Antarctic region, as it is the primary food source for fish, whales, seals, flying birds, penguins and cephalopods. The high concentrations of the species and its possible uses -food for human and animal consumption and in the production of industrial, pharmaceutical and dietetic products- generates interest in the fishing industry. Its relevance motivated the implementation of administrative measures and international regulations for this fishery, which are summarized in this review. Chile is the only South American fishing country that has shown interest in participating in Antarctic krill fishery. Thus, between 1983 and 1994, the Fisheries Development Institute and some companies carried out fishing activities mainly aimed at prospecting and researching this species. However, starting in 2011, the factory trawler Betanzos began sustained commercial krill fishing aimed at krill meal production. This document analyzes the information collected by said vessel between 2011 and 2016, including areas of operation, fishing depth catches and CPUE obtained. Also, the main challenges faced by this fishery and the actions planned as solutions are assessed.
This report presents the results of a method used to explore potential explanatory variables influencing finfish bycatch in the krill fishery of Area 48. Records of finfish bycatch in the Area 48 krill fishery collected by observers on the FV Saga Sea were analysed over the period 2007/08-2011/12. The majority of fish caught were either small juveniles or larvae, dominated by Myctophidae (lanternfish) and Channichthyidae (icefish) with lower levels of Nototheniidae present. The influence of potential explanatory variables was investigated using a delta-lognormal modelling approach. Time of day, krill catch, sea surface temperature, bottom depth and fishing depth and season were all significantly associated with the presence of finfish bycatch in the Saga Sea krill fishery for at least one family and Subarea specific model, however, the majority of variables were not significantly correlated with the abundance of finfish bycatch. This may be partly due to the low numbers of hauls with positive incidences of bycatch of the finfish family groupings. Results indicated that there was a wide disparity in the influence of the explanatory variables on the presence of finfish in bycatch, which varies markedly by taxonomic grouping to the family level and CCAMLR Subarea. There were, however, some trends which persisted across Subareas and families, the most notable observed trend being the reduced likelihood of catching all families of finfish investigated in dense krill aggregations, which is consistent with the literature. These predictive models were used to estimate bycatch rates per tonne of krill catch for Channichthyidae, Nototheniidae and Myctophidae to predict total finfish bycatch of the Area 48 Saga Sea krill fishery and quantify the impact of this bycatch on the finfish stocks (Peatman et al., 2012).
Fisheries interactions with non-target marine vertebrates are a worldwide problem. The impact of coastal bottom trawl fisheries on marine mammals has never been evaluated before in the Río de la Plata estuary and adjacent Atlantic Ocean. Our aim was estimate the bycatch per unit effort (BcPUE) and incidental mortality rates of marine mammals caused by the industrial coastal bottom trawl fisheries fleet, evaluating the mortality of three species (i.e. Franciscana dolphin – Pontoporia blainvillei, South American sea lion – Otaria flavescens and the South American fur seal – Arctocephalus australis); these species are facing conservation problems either at regional or local scale. We conducted an on board data collection program of marine mammals’ bycatch involving crew members of 10 vessels (30%) of the Uruguayan coastal bottom trawl fleet between January/2009 and April/2012. A total of 102 marine mammal individuals were by-caught during 490 fishing trips involving 2,398 fishing days. Mortalities estimated for Franciscana dolphin were the highest among the species affected, with values adding up to ~100 individuals for year (with scenarios of population decline in the area), followed by Southern sea lion with ~77 individuals by year (0.8% of local population) and the Southern fur seal (Arctocephalus australis) with an annual mortality estimate of ~25 individuals (~0.02% of local population). BcPUE showed significant temporal variation, with Franciscana dolphin BcPUE varying seasonally and those of otariids according to their breeding season. Our estimates of marine mammal bycatch by bottom trawl fisheries should constitute an important input for sustainable management of fisheries and the conservation of marine biodiversity in the Southwestern Atlantic Ocean.
Chile holds globally important colonies of endangered and endemic seabird species, and globally vulnerable nonbreeding species visit its waters. One of the major threats for seabirds in Chilean waters is the impact of fishing activities, both industrial and artisanal, which overlap with seabird breeding and foraging areas. Bycatch in fisheries threatens 27 identified species and two groups of unidentified albatrosses and penguins, with the Black-browed Albatross Thalassarche melanophrys as the species most related to bycatch events. Responding to the international call for the voluntary adoption of a plan to reduce the impacts of fisheries on seabirds, Chile generated a National Plan of Action (PAN-AM/Chile) to monitor seabird bycatch, and to mitigate threats to seabirds with emphasis on industrial longline fisheries. Following the successful reduction of seabird bycatch in the demersal longline fishery for Patagonian toothfish Dissostichus eleginoides, with zero individuals caught during 2006, Chile is extending the PAN-AM/Chile to include other fisheries that use gear known to cause incidental mortality, such as trawl, purse seine, and gillnets. This initiative is supported by actions associated with the creation of a national scientific committee for biodiversity, and new collaborative research platforms under the auspices of the Chilean Undersecretariat for Fisheries and Aquaculture.
We analized the relationship between the variability in the rate of seabird bycatch in pelagic longline fishery for swordfish (Xiphias gladius), and several temporary, environmental, spatial and fisheries factors for the fishing period from 2007 to 2009. The results show that the fishing operations of this fleet mainly affect the albatross, group that accounts for 83.7% of the incidental catch of seabirds recorded in the period. This bycatch is due primarily to the presence of the South Pacific Subtropical Front, a system that causes the overlap between the activities of this fleet with the spatial distribution of these seabird species during the resident phase of the nonbreeding period. By the other hand, the variability in bycatch would be strongly linked to visual stimuli (measured by the percentage of chemical lights and percentage of squid) and the existing ambient lighting conditions during the set (measured by the lag time of sunset with respect to time start set and lunar phase).
The behaviour of seabirds and the rate of incidental mortality were observed during commercial trawling operations for Patagonian toothfish (Dissostichus eleginoides) in the 1994/95 season near Macquarie Island and Kerguelen Island. Longlining for D. eleginoides and trawling for mackerel icefish (Champsocephalus gunnari) were also observed at Kerguelen. Many seabirds were constantly observed near the vessels, especially giant petrels (Macronectes halli and M. giganteus), black-browed albatrosses (Diomedea melanophris) and Dominican gulls (Larus dominicanus). White-chinned petrels (Procellaria aequinoctialis) were common only at Kerguelen. Bird mortality during trawling was zero at Macquarie Island and very low at Kerguelen; most was associated with a single vessel using a netsonde cable while targetting C. gunnari. Most mortality associated with both longliners and trawlers was of white-chinned petrels, with a lesser mortality of albatross species. Mortality rates associated with longlining in the Kerguelen region were lower than those reported for the South Georgia area, probably because the birds at the former site are distracted from the longlines by the discharge of offal from the side of the vessel opposite to where the longline is set.
At the 2004 meeting of the Working Group on Ecosystem Monitoring and Management (WG-EMM) in Siena, Italy, the UK reported on the by-catch of fur seals (Arctocephalus gazella) in the krill fishery around South Georgia, and on mitigation methods that were being developed and deployed to avoid fur seal deaths in the fishery. WG-EMM requested that the UK provide further details of the methods employed for consideration by the ad hoc Working Group on Incidental Mortality Arising from Fishing (WG-IMAF). Three CCAMLR international scientific observers recorded mitigation measures for fur seal entanglements on krill vessels fishing around South Georgia in the 2004 fishing season. The measures implemented were based on four approaches: physical barrier, barrier plus escape hatch, manufactured seal-exclusion devices and gear configuration. Those vessels initially without mitigation measures were able to introduce them without further cost and minimal disruption to fishing activity during the season. These approaches, aimed at reducing seal entanglements, are similar to the two systems implemented by Japanese vessels during the 2003 krill fishing season around South Georgia (Japan Deep Sea Trawlers Association, 2004).
Armstrong (1995) presented a final report of scientific observations conducted aboard the Japanese krill fishing vessel Ckiyo Maru No. 2. Unfortunately, Armstrong's fish by-catch data were not presented in a standardised manner. This paper presents a brief re-analysis of the by-catch data collected on board the Chiyo Mnru No. 2; means and variances are calculated from the delta distribution. In numbers, an average of about 14 fish were caught per tome of krill, and an average of about 25 fish were caught per hour of towing. In weight, an average of about 1.2 kg of fish were caught per tonne of krill, and an average of about 2.2 kg of fish were caught per hour of towing. Confidence intervals for mean by-catch estimates are wide suggesting that, in the future, more hauls should be sampled for by-catch. The proportion of hauls containing fish was much higher for the Ckiyo Maru No. 2 than it was for other Japanese and Ukrainian krill trawlers fishing in the Atlantic sector of the Southern Ocean. This difference may be related to differences in the amount of krill that was subsampied for making observations on fish by-catch. The by-catch data from the Ckiyo Maru No. 2 did not provide a clear picture of the reiationship between haul-specific fish by-catch and the catch rate of krill, and this observation is different from those made in most other studies. It would be worthwhile to estimate an appropriate sample size (in numbers of hauls) and subsample size (as a fraction of haul-specific krill catches) for observers collecting data on fish by-catch.
This paper discusses an investigation of juvenile Antarctic fish caught during krill fishing by the FV Grigoy Kovtun in the area around South Georgia from May to July 1992. Two species were predominant in the by-catches: Charnpsocephalus gunnari and Nototheniops larseni. The frequency of occurrence of juvenile fish was 18.2% when all krill tows were included and 45.5% when only tows made in shelf waters were considered. The abundance of juvenile fish in catches, normalised to one tonne of krill, ranged from 700 to 18 900 individuals. In the case of C. gunnari, average values were 966 k 225 ind./tonne krill and 2 434-c 579 ind./tonne krill for all trawls and for shelf trawls, respectively. For N. larseni the corresponding averages were 557 + 103 and 1 388 + 248. The mean standard length of C. gunnari was 68.5 to 79.