Fishing – APECS Portugal

Distribution and ecology of the four Macrourus species by-caught in the longline fishery at South Georgia, Southern Ocean

APECS — Thu, 30 Apr 2026 16:08:18 +0000

South Georgia’s waters are among the most productive in the Southern Ocean, supporting longline fisheries that target Patagonian toothfish. However, during these operations, four species of grenadier Macrourus caml, Macrourus carinatus, Macrourus holotrachys and Macrourus whitsoni — are regularly caught as by-catch. Moreover, despite being commonly mentioned in fishing records, these species have until now been identified only to genus level, preventing any distinction between the four species. This aggregation masks the important biological differences between them and the true extent of the effects of by-catch.

In this study, researchers carried out the first comprehensive biological assessment of all four Macrourus species caught in South Georgia waters, using fishery and observer data collected between 2018 and 2022. By analysing distribution patterns, depth preferences, sex ratios and habitat associations, the team was able to characterise each species individually and assess their respective vulnerabilities to fishing pressure.

The results revealed striking differences between species. Three of the four showed female-biased sex ratios, which has direct implications for stock productivity and reproductive capacity. Each species also occupied a distinct depth range and geographic distribution: M. holotrachys was the most frequently caught and ranged widely between 1000 and 1750 metres; M. caml showed the greatest flexibility in habitat use; M. carinatus was concentrated in the western region; and M. whitsoni was rarer, found mostly in deeper waters beyond 1500 metres in the northeast and east.

These findings highlight a significant gap in how by-catch is currently managed. Reporting species collectively at genus level masks the fact that each faces different levels of risk, and that the health of the target fishery is not a reliable proxy for the condition of non-target species. The authors argue that species-level monitoring and accurate data collection are essential for setting meaningful by-catch thresholds and ensuring the long-term sustainability of toothfish fish fisheries across the CCAMLR area.

Figure1: Proportion (%) of females (F) and males (M) across depth (m) of the four Macrourus species by-caught at South Georgia (CCAMLR subarea 48.3) longline fishery from 2018 to 2022.

Source:Abreu, José, et al. “Distribution and ecology of the four Macrourus species by‐caught in the longline fishery at South Georgia, Southern Ocean.” Journal of Fish Biology (2026).

Author: Lucas Bastos

How important is Antarctic krill and the task to manage it?

APECS — Fri, 15 Sep 2023 23:11:00 +0000

Most of the human population does not know and has probably never heard of the Antarctic krill species (Euphasia superba). However, this small marine species is designated by many scientists as the most important in the food web of the Southern Ocean, which surrounds the entire Antarctic continent. Antarctic Krill is a small crustacean, like a “mini-shrimp” (figure 1), however its biomass is estimated to be between 300 and 500 million tons, which makes it the largest biomass of any multicellular species in the world. The Atlantic sector part of the Southern Ocean contains 70% of the population.

Figure 1. Antarctic Krill (Euphasia superba).

Thus, both due to their enormous quantity and the high energy values they contain (e.g.: omega 3), krill are the main prey for countless Antarctic species, from penguins, seals, whales, fish and many other species of albatrosses and petrels. In some of these species, krill can even represent more than 70% of the diet. Its ecological importance is therefore undeniable in this large ecosystem.

Finally, and as mentioned above, krill is an animal with characteristics that are also very beneficial for humans through medicines, as well as for other activities through fishmeal/aquaculture or natural fertilizers. In this way, there is a very active fishery that targets krill, making its management laborious and highly special.

Krill fishing has existed for over 50 years, mainly around the Antarctic Peninsula and the South Shetland Islands, South Orkney Islands and South Georgia. Initially more focused during the summer, it moved progressively to mainly operating in the winter. A measure aimed at avoiding competition between fishing and predators during the breeding season.

Its management is carried out by the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR), which is based on biomass surveys. This is a representative sample of the potential biomass in a given area, then stipulating a maximum quota of krill. As a prevention and sustainability focus, CCAMLR states that 75% of the original biomass is maintained.

So, what is the difficulty in this management?

Much of the discussion about krill fishery management in CCAMLR has focused on protecting krill predators that breed on land and fishing operations.

On the other hand, in recent times, there has been relatively little discussion about the risks that fishing poses to the krill population itself. The view of sustainability to date is now challenged by the high levels of variability observed in available indices of krill abundance, particularly over the last two decades, which vary in magnitude and increasing fishing space, resulting in substantial local impacts.

Although the reproduction cycle is considerably known and studied, krill are quite dependent on both ocean currents, plus the locations and environmental conditions where juveniles develop. Hence, being where the problem lies today. With current climate change or the increasingly strong decline of sea ice, crucial in its development, krill recruitment has varied strongly between years, and this is expected to be subsequently reflected in the available biomass. Much of the previous research was carried out mainly in the summer, leaving a gap in its cycle in the winter phase. Fishing itself has evolved and today its capacity to extract krill from the water both spatially and in quantity is much faster, having much more sudden impacts on the population. In addition, this decreases in sea ice, opens new areas available to the fishing industry, which generate more pressure. The key thus lies in understanding the krill reproduction and development cycle with present environmental conditions and future perspectives. Both science and the fishing industry must work hand in hand, so that we have the most real value of the total krill biomass, and thus adjust and apply the best measures. In the end, is of upmost aim that the benefits for humans never corrupt the ecological and biological importance that this fantastic species has for the Southern Ocean and the entire Antarctic region.

Author: José Abreu

Source: Meyer, B., Atkinson, A., Bernard, K.S. et al. Successful ecosystem-based management of Antarctic krill should address uncertainties in krill recruitment, behaviour and ecological adaptation. Commun Earth Environ 1, 28 (2020). DOI: 10.1038/s43247-020-00026-1

Impacts of Southern Ocean Fisheries on wandering albatross populations

APECS — Thu, 15 Jun 2023 23:48:22 +0000

Fisheries play a critical role in the conservation of many marine vertebrates, whether by bycatch, collision with vessels, or overfishing their food resource. An example of marine vertebrates that face this threat are the albatrosses. Albatrosses are seabird species that are scavenger opportunists and are attracted to fishing vessel’s discards. They have a broad range of scavenging, which puts them at risk by fisheries in national and international waters. A species affected by the threats mentioned above is the wandering albatross (Diomedea exulans). The wandering albatross population in South Georgia has been declining rapidly since the 1970s.

To study the interactions between the wandering albatross and Southern Ocean fisheries, radar GPS-loggers were attached to the seabird individuals, along with information regarding the position and movements of fishing vessels. This study considered the different life stages and sex of the wandering albatross, which are usually under-researched or not considered in many studies.

The results showed that different types of gear used in fisheries make the visiting of the wandering albatross differ. The fisheries that use set (demersal) longliners had a higher likelihood of being visited by this seabird than other gear types (mainly trawlers, squid jiggers and drifting longliners).

When analysing the bycatch rate of different life stages of the wandering albatross, the results showed an increase in the visits of fishing vessels by the wandering albatross during the incubation period (Fig. 1). However, it’s important to note that if discards are not occurring this seabird won’t visit the vessel, in the case that prey is available in the surroundings.

Fig.1 – Effects of life-history stage and status on the visiting behaviour (time spent within 5 km of a vessel) of wandering albatrosses tracked from South Georgia.

In order to reduce mortality bycatch associated with fisheries of the wandering albatross and other vulnerable seabird species, it’s important to engage with the managers and operators of the main fisheries that come in contact with these species and implement best practices regarding seabird-bycatch mitigation, seabird bycatch rates and monitoring of compliance.

Source: Carneiro, A. P. B., Clark, B. L., Pearmain, E. J., Clavelle, T., Wood, A. G., & Phillips, R. A. (2022). Fine-scale associations between wandering albatrosses and fisheries in the southwest Atlantic Ocean. Biological Conservation, 276. DOI: https://doi.org/10.1016/j.biocon.2022.109796

Author: Mariana Quitério

Bottom Trawling and the Sponge community in the Barents Sea

APECS — Thu, 15 Sep 2022 18:50:00 +0000

Bottom trawling, as its name implies, consists of a large conical net with a wide mouth and a small, closed end. In this type of fishing, the result is the capture of a large number of fish. In one hand, trawling fills supermarket shelves, yet it also empties the seabed. Plus, the decreasing of marine fauna and flora caused by this type of fishing, has already reached one of the most remote places on the planet, the Barents Sea (Arctic Ocean).

Barents Sea is an extremely rich habitat, with high primary productivity, making this place an important habitat for numerous species, such as marine sponges. Here, it is possible to find a large community of marine sponges, such as GeodiaBarretti. These are considered fundamental to the habitat and serve as natural indicators of Vulnerable Marine Ecosystems. However, the increasing rate of trawling is also increasing the damage to the sea floor, which is often irreversible.

Figure 1. Geodia Barretti, a species of sponge that can be found in the Barents Sea.

This study aimed to analyze the effects of trawling on the abundance of Geodia spp. and diversity of associated fauna species. Therefore, were used images collected by an ROV (Remotely Operated Vehicle), of two locations with completely different levels of drag (location with low and heavy impact), which were compared. Through the analysis between the two locations, it is possible to verify the consequences that long-term trawling creates. In the place where trawling is not so frequent, it was possible to find a relatively diverse and abundant sponge community, in contrast to the place where trawling is more frequent.

Figura 2. Impacto da pesca de arrasto nas comunidades onde (a) não é frequente (b) é frequente.

Several studies have shown that the continuity of trawls in the same location leads to functional changes in benthic communities. Sponges have a high filtration rate, which allows them to remove a large amount of particles from the environment, including viruses and other pathogens. However, if the intensity of trawling continues to increase, and consequently to a decrease in the abundance of sponges in the Barents Sea, this habitat will experience an increase in the amount of particulate carbon deposited on the seafloor. With the increase in carbon, this location becomes more favourable for species that feed on dead organic matter. Which in turn leads to a change in the functional diversity of the system.

The authors concluded that bottom fishing significantly reduces sponge communities, reduces sponge abundance and size, and creates a change in species and functional diversity, and subsequently in ecosystem function and services.

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Source:Colaço, A., Rapp, H. T., Campanyà-Llovet, N., & Pham, C. K. (2022). Bottom trawling in sponge grounds of the Barents Sea (Arctic Ocean): A functional diversity approach. Deep Sea Research Part I: Oceanographic Research Papers, 183, 103742.

Author: Eva Lopes

The long road to recovery, decades after intensive fishing activity

APECS — Mon, 15 Nov 2021 01:39:00 +0000

Marine resources are among the most important resources for humanity, whose demand will continue to increase as population increases. Consequently, effective and sustainable management is essential, as is learning from the past. Many fish species have been or are overexploited, and depending on their characteristics, they can recover partially, completely, or even not recover from this overexploitation.

In the Southern Ocean, fishing is now regulated and with effective management measures. However, this was not always the case, and in the 1960s and 1970s, on islands such as South Georgia or Kerguelen there were intensive fisheries, including the fishery of marbled rockcod (Notothenia rossi). This fish species inhabits between 0 and 400m deep and reaches an average length of 50 – 70cm. For example, over the years of 1969 and 1971, around 500 000 tons of captured fish were reported at South Georgia. Although this catch was likely included other species other than rockcod, it still represents a large catch. Additionally, part of the fishing was also illegal and incorrectly reported. All these factors dictated the depletion of this stock, which has dropped drastically, almost leading to the disappearance of marbled rockcod populations. Due to this, the fishery was no longer profitable as it was also banned, both in South Georgia and later in the Southern Ocean, an end dictated by the Commission for the Conservation of Living Marine Resources of Antarctica (CCAMLR).

A study by British researchers based on data from 23 years of sampling through research vessels, explored how the population of this species has or not recovered 50 years after its overexploitation. This analysis was performed based on numerous variables, from abundance, distribution, size, weight and age of individuals, sexual maturity, as well as their diet.

Catches of rockcod (biomass, here defined as the weight (whole-body, wet weight)) in the South Georgia region from 1966 to 1985. FAO – Food and Agriculture Organization of the United Nations

Recovered population?

The researchers found that marbled rockcod population has managed to recover and restore healthy levels. However, such recovery only began after 2005, 35 years after the overexploitation. It has taken 3 to 4 generations (6-8 years per generation) for the population to stabilize and be able to gradually grow. Several factors are associated with this recovery as well as with its possible delay. Among these are the fishery ban, the plasticity of their diet and the occupation of new areas with more prey. The delay of several decades for this recovery is attributed in part to the late sexual maturity in this species, the recovery of a considerable predator during this period, the Antarctic fur seal (Arctocephalus gazella), and the possibility that the South Georgia ecosystem may not have the same carrying capacity to sustain as much biomass as in the 60s and 70s, due to the environmental changes that have been impacting the region.

Therefore, despite past errors in the Antarctic Ocean, in this case South Georgia, this study shows that after implementing science-based management and strict measures it is possible, in the long term, for a species to recover and establish itself again in the ecosystem. A model that can serve as an example for other places.

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Source: Hollyman, Philip R., et al. “A long road to recovery: dynamics and ecology of the marbled rockcod (Notothenia rossii, family: Nototheniidae) at South Georgia, 50 years after overexploitation.” ICES Journal of Marine Science 78.8 (2021): 2745-2756. DOI: 10.1093/icesjms/fsab150

Author: José Abreu

Fishing patterns affect depredation interactions of longline fishing-odontocetes in Southern Ocean

APECS — Tue, 15 Oct 2019 17:45:32 +0000

Fishing methods have evolved and changed over the years. With the decline in landings and effects of climate change, fishing methods became more selective, especially toward longline fishing. However, this method is associated with increased depredation interactions with odontocetes (toothed whales). Depredation interactions occur when a wild species consumes a resource that is caught or grown/raised by humans. When interacting with fishing vessels, odontocetes remove the fish directly from the hook which affects stock assessment and thus conservation efforts for fish species, as well as conservation of odontocetes due to potential lesions or even death. In the Southern Ocean, longline fishing is used to catch Patagonian toothfish (Dissostichus eleginoides), the most important economic activity in the region.

A recent study looked at the effects of fishing patterns in depredatipn interactions between longline fishing vessels and two odontocete species, orcas (Orcinus orca) and sperm whales (Physeter microcephalus) in the Antarctic Ocean. Data was collected in longline fishing vessels in seven different study areas: southern Chile, and around the Falkland, South Georgia, Prince Edward Island and Marion (PEMI), Crozet, Kerguelen, Heard and MacDonald Islands (HIMI) islands.

The results obtained showed that the two species interact with the vessels differently, depending on extension and depredation opportunities. The increase in fishing effort during the winter, especially in HIMI and South Georgia, coincided with a decrease in depredation interaction with sperm whales, probably due to the low number of individuals in this region. For this species, a decrease in interactions was observed from 2003 to 2015 near Chile, Crozet and Kerguelen Islands, but an increase was observed near Falkland Islands. For orcas, there was a decrease in interactions near Chile, but an increase in South Georgia.

In relation to fishing areas, in larger areas depredation interactions were reduced of both orcas and sperm whales with vessels, likely due to reduced probability of vessel detection by the whales. Higher vessel mobility lead to a decrease in interactions with orcas. However, the opposite was observed for sperm whales likely due to highest density of individuals, except for HIMI. In this region, depredation interactions were only reported once in 2010, year at which the fishing season was extended until the Spring, when sperm whales migrate to the region.

Some vessels were equipped with “cachalotera”, a fishing system that prevents whales from catching the fish from the hooks. Yet, the results showed no effect of this system in depredation interactions, and these even increased in some cases. The whales were still able to get fish and the vessels ended up remaining in the region to fish for longer.

Lastly, the depth at which the vessels fish influenced the probability of encounters with orcas and sperm whales, that is, these species tend to be distributed in shallower areas used by vessels. This can also be related to oceanographic conditions, i.e. the abundance of prey may be higher in shallower waters for both fishing and depredation. It is important to improve fishing methods and control fishing vessels in these regions to mitigate this issue. Since sperm whales interact more with vessels, more attention should be payed to take conservation actions for this species.

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Source: Tixier, P., Burch, P., Richard, G., Olsson, K., Welsford, D., Lea, M. A., Hindell, M. A., Guinet, C., Janc, A., Gasco, N., Duhamel, G., Villanueva, M. C., Suberg, L., Arangio, R., Söffker, M., & Arnould, J. P. Y. (2019). Commercial fishing patterns influence odontocete whale-longline interactions in the Southern Ocean. Scientific reports, 9(1), 1904. DOI: 10.1038/s41598-018-36389-x

Author: Inês Ribeiro