Local Fish Stocks Research Articles

Multi‐year monitoring shows higher species richness and diversity of fish assemblages in a Danish seagrass meadow as compared to neighbouring non‐vegetated areas

AbstractSeagrass meadows provide an important nursery and feeding habitat for fish, globally. However, limited data exist on how these vegetated coastal ecosystems affect local fish stocks over longer time periods. By means of beach seine hauling with a bio‐monitoring seine net, we collected fish data in Kronborg Bay (Denmark) over 4 years. The bay contains both vegetated and bare sediment areas in close proximity to Kronborg Castle in Elsinore and is part of the Øresund strait; a dynamic marine environment linking the Baltic Sea with the inner Danish waters (Kattegat). We investigated the biodiversity and fish abundance in a healthy seagrass meadow and compared it with a bare adjacent sediment area. We show that seagrass is important for fish species like the Atlantic cod, the two‐spotted goby, and the broadnosed pipefish. The seagrass meadow harboured more fish species and higher biodiversity, while the number of individuals was higher in the adjacent bare sediment area as a result of high abundances of lesser sand eel. Pilou's evenness and the Shannon‐Wiener index showed 2–4‐fold higher biodiversity in the seagrass meadow. The seagrass meadow harboured about 35% more fish species than the bare adjacent sediment. The Atlantic cod was almost entirely found in the seagrass meadow, while lesser sand eel that showed an overall increase in abundance in both habitats, represented the largest proportion of the total number of fish individuals (up to about 60%) and was mostly found on the bare adjacent sediment. Species abundance was analysed for changes over time, where, for example the European plaice showed an increase in abundance over the 4‐year period of investigation. Seagrass meadows can thus be very important for the Atlantic cod population in the Øresund strait and generally for local fish productivity, abundance and diversity.

Increasing trammel mesh size reduces biomass removal, mitigates discards and increases economic revenue in artisanal fisheries

Small-scale fishing plays a major role in regional economies worldwide and, with a large number of small vessels involved, it provides employment and livelihood to coastal communities. Generally recognized as more selective than other fishing practices, small-scale fishery can nevertheless be subjected to high rates of discards of both non-target species and small-sized individuals, which in turn could lead to both decreased incomes for fishers and increased depletion of fish stocks. However, if the relationship between fish size and price has long been assessed, the effect of enhanced size-selectivity of fishing gears and consequent economic gains has been little investigated. This study, set in the Porto Cesareo Marine Protected Area (Italy, Ionian Sea), aimed at testing effective strategies to improve trammel net selectivity, reducing discards and maximizing the income for fishers. Different mesh sizes (20, 22 and 24 mm) trammel nets were employed. The study consisted in 72 fishing days from July 2012 to September 2013 and each day involved experimental fishing with the three mesh sizes. A total of 16008 specimens (103 species) were collected but the analysis focused on the 18 most common species in the area for a total of 12782 individuals. Mesh size trammel nets of 20 mm and 22 mm yielded most of the biomass, 324.8 and 321.5 kg respectively, while the 24 mm mesh yielded 280.7 kg. The 24 mm mesh, even if accounted for lower income compared to the 22 mm mesh (2383.9 € vs 2590.5 €, respectively), provided significant 50% reduction of discards compared to the 20 and 22 mm mesh. The use of 24 mm mesh size was found to be an effective strategy to reduce the number of discarded organisms and, consequently, the pressure exerted on local fish stocks with associated higher revenue for fishers. The results of this study demonstrated that trammel net selectivity can improve and support conservation measures and concurrently increase profitability of local fishery.

The Lobo-lobo fry fishery in the western Visayan Sea, Philippines: Abundance, catch composition, and potential fisheries impact

Lobo-lobo are small fishes that are caught using fine mesh nets in the western Visayan Sea whose market extends outside of the Visayan Sea, and perhaps even outside of the country. With high consumer demands, it is targeted year-round. Catches of fine-meshed boat seines operating in the waters off Concepcion, Iloilo which target large amounts of small and early juvenile fishes were monitored daily from June to December 2016 and June 2020 to October 2021. Results showed that catches were comprised of several species and clearly show the selection for early juveniles by the lobo-lobo fishery. At least 53 families comprise the lobo-lobo catches, dominated by Engraulidae (78.5%) and Clupeidae (13.1%), and are mostly comprised of post-larvae and early juveniles with sizes ranging from 0.2 to 3.6 cm standard length. The estimated total annual catch of the local boat seine fleet during the study period ranged from 313.8 mt to 869.0 mt. The fishing operations are concentrated between Tago and Igbon Islands and appear to be consistent throughout the year, but the composition and proportion of catches differed seasonally. This area appears to be a critical habitat, supporting the growth and survival of several species. Protecting this area and restricting the use of fine-meshed nets targeting fry will likely have an overall positive impact on the local fish stocks.

Fishing activities shape the flight behaviour of an opportunistic predator species

Human activities provide opportunistic species with abundant and predictable feeding opportunities that may shape their ecology, including their movement patterns and behaviour. Investigating human-wildlife interactions in marine ecosystems is challenging because of the logistic constraints of surveying vast and remote geographical areas. Fortunately, miniaturized biologging devices now provide the possibility of assessing the influence of human activities on marine life, particularly in the case of large-sized predators. Here, we used GPS tracking data for Mediterranean endemic Audouin's gulls, Ichthyaetus audouinii, to quantitatively characterise gulls' foraging trips and evaluate individuals' foraging behaviour in relation with fisheries. By using ca. 38,090 space-time locations (i.e., 362 foraging trips), we calculated eight flight behaviour movement metrics to describe gull's flight behaviour within foraging trips. We used these movement metrics to analyse individuals' flight behaviour in contrasting fishing activity scenarios (i.e., presence/absence of fishing activity by trawlers and purse-seiners) and in response to spatial-temporal co-occurrence with fishing vessels operating in the area. Our results showed that Audouin's gulls adapted their flight behaviour in response to fisheries. When fishing vessels were active (particularly trawlers), gulls flew faster (particularly when co-ocurring with a fishing vessel) and more directly (i.e. lower directional changes), compared to non-fishing situations or when temporally co-occurring with purse seiners. This work enhances our understanding on seabird-fishery interactions, and may contribute to further evaluations on species responses to resource shortage scenarios, such as the collapse of local fish stocks and landing obligations. Beyond this ecological information, our results may also contribute to the use of seabirds for monitoring fisheries, and help fight Illegal, Unreported and Unregulated fishing (IUU) in areas where fishing vessels cannot be monitored by other means (e.g., through Vessel Monitoring Systems -VMS- or Automatic Monitoring Systems -AIS-).

Can global aquaculture growth help to conserve wild fish stocks? Theory and empirical analysis

AbstractCan fed aquaculture growth alleviate overfishing and foster the conservation of wild fish stocks? To examine this question we present a stylized fishery model of trade in edible fish and fishmeal that incorporates both market linkages and biological (predator–prey) linkages between the aquaculture sector and capture fisheries. We study the effects of local aquaculture growth, as induced by an increase in aquaculture feed‐efficiency (technology shock), and of external or global aquaculture growth as experienced by either a drop in the price of edible fish or as an increase in the price of fishmeal (price shocks). While domestic (or “local”) aquaculture growth increases wild fish stocks due to positive market interactions, the effects of external (or “global”) aquaculture growth are generally ambiguous and depend on the strength of biological linkages. A stylized empirical application of the cod (predator) and capelin (prey) fisheries in the Barents Sea illustrates that the biological linkages between cod and capelin reduce the positive impact of aquaculture on cod conservation roughly by 50%.Recommendations for Resource Managers: Fishery managers should differentiate between the effects of local, technology‐driven aquaculture growth and the effects of global, price‐driven aquaculture growth. The latter may have negative impacts on local fish stocks and the economy. Real fishmeal prices increased substantially since the year 2000. For multispecies fisheries that are not properly managed, this can increase pressure on fish stocks if predator–prey linkages are strong, if prey species regeneration is slow, and if pelagic prey species are relatively easy to catch. An empirical application shows that predator–prey linkages reduce but not overthrow the positive effects of global aquaculture growth on the conservation of local predator fish stocks. This provides some evidence that a reallocation of fishing effort from higher to lower trophic levels can conserve fish stocks at higher trophic levels.

Evaluating sustainable development policies in rural coastal economies

Sustainable development (SD) policies targeting marine economic sectors, designed to alleviate poverty and conserve marine ecosystems, have proliferated in recent years. Many developing countries are providing poor fishing households with new fishing boats (fishing capital) that can be used further offshore as a means to improve incomes and relieve fishing pressure on nearshore fish stocks. These kinds of policies are a marine variant of traditional SD policies focused on agriculture. Here, we evaluate ex ante economic and environmental impacts of provisions of fishing and agricultural capital, with and without enforcement of fishing regulations that prohibit the use of larger vessels in nearshore habitats. Combining methods from development economics, natural resource economics, and marine ecology, we use a unique dataset and modeling framework to account for linkages between households, business sectors, markets, and local fish stocks. We show that the policies investing capital in local marine fisheries or agricultural sectors achieve income gains for targeted households, but knock-on effects lead to increased harvest of nearshore fish, making them unlikely to achieve conservation objectives in rural coastal economies. However, pairing an agriculture stimulus with increasing enforcement of existing fisheries' regulations may lead to a win-win situation. While marine-based policies could be an important tool to achieve two of the United Nations Sustainable Development Goals (alleviate poverty and protect vulnerable marine resources), their success is by no means assured and requires consideration of land and marine socioeconomic linkages inherent in rural economies.

A Major Ecosystem Shift in Coastal East African Waters During the 1997/98 Super El Niño as Detected Using Remote Sensing Data

Under the impact of natural and anthropogenic climate variability, upwelling systems are known to change their properties leading to associated regime shifts in marine ecosystems. These often impact commercial fisheries and societies dependent on them. In a region where in situ hydrographic and biological marine data are scarce, this study uses a combination of remote sensing and ocean modelling to show how a stable seasonal upwelling off the Kenyan coast shifted into the territorial waters of neighboring Tanzania under the influence of the unique 1997/98 El Niño and positive Indian Ocean Dipole event. The formation of an anticyclonic gyre adjacent to the Kenyan/Tanzanian coast led to a reorganization of the surface currents and caused the southward migration of the Somali–Zanzibar confluence zone and is attributed to anomalous wind stress curl over the central Indian Ocean. This caused the lowest observed chlorophyll-a over the North Kenya banks (Kenya), while it reached its historical maximum off Dar Es Salaam (Tanzanian waters). We demonstrate that this situation is specific to the 1997/98 El Niño when compared with other the super El-Niño events of 1972,73, 1982–83 and 2015–16. Despite the lack of available fishery data in the region, the local ecosystem changes that the shift of this upwelling may have caused are discussed based on the literature. The likely negative impacts on local fish stocks in Kenya, affecting fishers’ livelihoods and food security, and the temporary increase in pelagic fishery species’ productivity in Tanzania are highlighted. Finally, we discuss how satellite observations may assist fisheries management bodies to anticipate low productivity periods, and mitigate their potentially negative economic impacts.

An integrated bioeconomic local economy-wide assessment of the environmental impacts of poverty programs

A new generation of poverty programs around the globe provides cash payments to poor and vulnerable households. Studies show that these social cash transfer programs create income and welfare benefits for poor households and the local economies where they live. However, this may come at the cost of damaging local environments if cash payments stimulate food production that conflicts with natural resource conservation. Evaluations of the economic impacts of poverty programs do not account for the welfare consequences of environmental impacts, which are potentially large for poor communities closely tied to natural resources. We use an ex-ante policy simulation tool, a bioeconomic local computable general equilibrium model parameterized with microsurvey data, to analyze the expected welfare consequences of environmental degradation caused by a cash transfer program. For a Philippine fishing community that is a net importer of fish, we show that a government cash transfer program initially increases real incomes for all households. However, increased demand for fish leads to a decline in the local fish stock that reduces program benefits. Household groups experience declines in real income benefits of 2-63%, with fishing households suffering the largest declines. Impacts on local fish stocks depend on the extent to which markets link fishing communities to outside regions through trade. Greater market integration can mitigate the fish stock decline, but this reduces the local income benefits of cash transfers.

Domestic landings and imports of seafood in emerging economies: The Brazilian sardines market

Seafood imports have increased strongly in emerging economies during the last decades. However, the impacts of increased imports on price determination process, local fishers' income and fish stocks have received limited attention. This paper presents a market integration and price transmission analysis for the Brazilian sardine market, comprising the fresh and canned sardines segments, to shed light on these issues. Imports currently supply about one-half the sardines in the Brazilian market, and even more when the domestic fishery landings are low. The results suggest not only a fully integrated market but also a complete price transmission in both sardine value chains. Hence, import competition with domestic fisheries limit price increases in the domestic fishery and reduce fishers' income and fishing effort. However, the canneries, consumers and fish stocks are better off.

Aquaculture, fish resources and rural livelihoods: a village CGE analysis from Namibia’s Zambezi Region

Aquaculture is widely recognised as a way to reduce malnutrition and poverty. So far, research has mainly focused on Asia, and the few studies available from sub-Saharan Africa are predominantly ex-post partial analyses. By constructing a village computable general equilibrium (CGE) model, we aim to investigate whether aquaculture improves local livelihoods and simultaneously has the potential to counteract local overfishing. We apply this to a rural case study region in Namibia where malnutrition, poverty and fish resource overexploitation are current problems. Our village CGE model shows that aquaculture would be a viable livelihood activity improving household incomes and utility through labour reallocations. Furthermore, aquaculture can counteract malnutrition through increased fish consumption. Higher opportunity costs lead to households leaving the fisheries and switching to aquaculture. These substitution effects offer the possibility of reducing the pressure on local freshwater fish stocks. Policy makers can use the results to introduce aquaculture interventions in rural areas. Our findings indicate that such interventions should take particular account of the poorest households, which are most dependent on fisheries. The derived opportunity costs provide information about payments that are necessary to make policy interventions acceptable for different household groups.

Recreational fisheries in Portofino Marine Protected Area, Italy: Some implications for the management

AbstractSince the 1970s, recreational fishing has become a mass hobby in Italy, reaching a large number of people, who, using modern equipment, increased their harvesting capacity, provoking serious conflicts with the professional fisheries. Recreational fishing is strictly regulated inside Italian Marine Protected Areas (MPAs) and is generally allocated to local residents, mainly to reduce the tensions caused by limitations of access to the resources. The aim of this study was to provide an analysis of recreational fishing activities within the Portofino MPA (Mediterranean Sea), to assess the possible impact on the local fish stocks and to plan potential management actions. Furthermore, some serious inconsistencies on the minimum lengths of fish caught as defined by law relative to the minimum size of first reproduction are discussed. Since 2014, all anglers exploiting the Portofino MPA have been obliged to fill out a logbook. The compilation of these was not completely satisfactory, when compared with a group of reliable anglers whose catches were accurately monitored, but allowed for estimated yields of about 24 kg/angler/yr. After 15 years of protection, the fish biomass has increased within the Portofino MPA, generating a positive spillover effect. At the same time, it has attracted many anglers whose gross harvesting was estimated at about 8 t/year, representing about the 8% of the total yield of the local small‐scale fishery.

The “easy restriction” syndrome drive local fish stocks to extinction: The case of the management of Swedish coastal populations

Spatially sensitive management built on detailed biological and socio-economic knowledge is required to establish sound fishing regulations and to avoid extinction of small coastal populations of fish and shellfish. Highly productive isolated populations of several commercial species have historically inhabited the Swedish west coast, but during the past century these populations have been depleted by fisheries and with no sign of recovery. Since 1999 several fisheries regulations and different stakeholder co-management initiatives have flourished along the Swedish coast of the Skagerrak. They aimed to facilitate the recovery of collapsed local stocks but the established regulations failed to identify and restrict the main sources of mortality acting on local stocks and they have thus been ineffective to promote the recovery. Furthermore, regulations have operated on the weakest among stakeholders (e.g.. recreational fishers), which have minor influence over management, and the restrictions have been imposed without providing any data which supported the choice (i.e. the “easy restriction” syndrome). In line with the general “spirit” of recent Swedish fishery management, we conclude that managers, without the disapproval of Swedish scientists, have circumvented limitations which should address the largest mortality factor, i.e. the commercial fishery. The regulations presently in place, have been politically uncontroversial and easy to implement, but have been highly unsuccessful. We therefore suggest that stakeholders, including politicians, should start focusing on more effective and science-based management and less on what is politically attractive if Swedish citizens shall have a chance to witness the recovery of their once flourishing coastal populations.

Evaluation of Different Aquaculture Feed Ingredients in Indonesia Using Life Cycle Assessment

Indonesia’s aquaculture industry has grown by almost 25% annually over the last five years, an achievement enabled through the increased use of commercial aquaculture feeds, made from agricultural, capture fisheries and livestock resources. The reliance of aquaculture on capture fisheries has, however, attracted criticism, as has the land use consequences of imported Brazilian soybeans. Sourcing more sustainable resources has thus become part of maintaining a good environmental image and to secure long-term growth. In the present study we applied LCA to a number of feed ingredients used by the Indonesian aquaculture industry, including local fishmeal, rice and maize, as well as imported soybean, wheat and livestock byproduct meal (BPM). The impact categories global warming, acidification, eutrophication, land occupation and freshwater consumption were evaluated. Shrimp byproduct meal was generally associated with the largest emissions, followed by poultry byproduct meal. Wheat bran from Australia was the agricultural product with the largest acidification impacts, while rice bran had largest freshwater requirements. Overall, however, a shift is needed away from the overexploited local fish stocks towards alternative substitutes.

Preliminary study of the sea surface temperature (SST) at fishing ground locations based on the net deployment of traditional purse-seine boats in the northern waters of Aceh — A community-based data collection approach

Reconstruction projects after the Indian Ocean Tsunami of December 26, 2004 were typically contracted out to implementing partners or government agencies. One of the few projects directly implemented by the Body of Rehabilitation and Reconstruction (BRR) was funded by the Asian Development Bank (ADB) to help reestablish fisheries. During the course of the project, 151 GPS-enabled depth sounders with data-logging devices were installed on various types of artisanal fishing boats engaged in the different types of fishing strategies in Aceh such as purse-seine, drop-line, long-line, and gill net fishing. These devices were configured to automatically record time, position, speed, water depth, and sea surface temperature (SST) every time the boat moved 30 m. This study examines the relationship between the sea surface temperature (SST) and the net deployment (ND) of traditional purse seine fishers. The data consists of 922 data sets (6,170,648 data points) collected from 45 purse seine boats between June 2007 and May 2009. Among the data, 1,619 data points indicated the total number of ND; the nets were deployed only when schools of fish were actually sighted. The results indicate that the most frequent SST for ND is 28–28.5°C±0.1365°C with a mean standard error of 0.0117% in a 95% confidence interval. This study has demonstrated that the data gathered from the fishermen (community-based approach) has near-real-time character and, consequently, is an important source for the monitoring and managing of the local fish stocks.

Jellyfish fisheries in the Americas: origin, state of the art, and perspectives on new fishing grounds

Jellyfish (primarily scyphomedusae) fisheries have a long history in Asia, where jellyfish have been caught and processed as food for centuries. More recently, jellyfish fisheries have expanded to the Western Hemisphere, often driven by demand from Asian buyers and collapses of more traditional local fish stocks. Jellyfish fisheries have been attempted in numerous countries in North, Central, and South America, with varying degrees of success. Here, we chronicle the arrival of jellyfish fisheries in the Americas and summarize relevant information on jellyfish fishing, processing, and management. Processing technology for edible jellyfish has not advanced, and presents major concerns for environmental and human health. The development of alternative processing technologies would help to eliminate these concerns and may open up new opportunities for markets and species. We also examine the biodiversity of jellyfish species that are targeted for fisheries in the Americas. Establishment of new jellyfish fisheries appears possible, but requires a specific combination of factors including high abundances of particular species, processing knowledge dictated by the target market, and either inexpensive labor or industrialized processing facilities. More often than not, these factors are not altogether evaluated prior to attempting a new jellyfish fishery. As such, jellyfish fisheries are currently expanding much more rapidly than research on the subject, thereby putting ecosystems and stakeholders’ livelihoods at risk.

When warming hits harder: survival, cellular stress and thermal limits of Sparus aurata larvae under global change

Understanding physiological and molecular compensation mechanisms that shape thermotolerance is crucial for estimating the effects of ocean warming on fish stocks, especially during early life stages, whose tolerance determines recruitment success and population viability. The aims of this study were to assess the sensitivity of fish larvae toward ocean warming and heat wave events in the commercial species, Sparus aurata, whose habitat is likely to be affected by rising water temperatures. We (1) estimated its critical thermal maximum (CTmax) and relative mortality upon warming, (2) quantified stress biomarkers: heat shock protein 70 kDa, total ubiquitin, antioxidant enzymes (superoxide dismutase, catalase, glutathione-S-transferase), lipid peroxidation and protein carbonylation, and (3) analyzed histopathological changes as a result of thermal stress. Larvae showed increasing levels of lethargy with increasing temperature, attaining a cumulative CTmax value of 30 °C. Relative mortality increased upon warming, reaching 80 % at 30 °C. Oxidative damage was higher at moderate temperatures and decreased at 24 °C probably due to a significant increase in superoxide dismutase’s (SODs) activity. Hsp70 chaperone levels also increased at 26 °C, but unfolding persisted at higher temperatures as shown by the increase in total ubiquitin at 26 and 28 °C, indicating protein damage. Skeletal muscle showed disorganization of muscle fibers from 24 °C onwards. Overall, protein denaturation seems to be the major cause of larval mortality, potentially compromising recruitment’s success from 22 °C onwards, since larvae migrate into nursery grounds by spring and summer (i.e., high temperatures), thus hindering the viability of local fish stocks. These data demonstrate that the biochemical homeostasis of fish can be disturbed within an ecologically realistic thermal range and emphasize the risks of rising global temperatures for larval fishes.

Diver operated video most accurately detects the impacts of fishing within periodically harvested closures

Periodically harvested closures (PHCs) have become the most common form of spatial management in Melanesia. Despite their popularity, their effectiveness to sustain local fish stocks remains largely unknown. Here we test the ability of non-destructive sampling techniques to detect the impacts of fishing in a PHC where harvest catch data provide an impact of known magnitude. We compared the ability of three commonly used techniques (underwater visual census, UVC; diver operated stereo-video, stereo-DOV; and baited remote underwater stereo-video, stereo-BRUV) to detect the impact of a harvest on fish assemblages within a PHC in Fiji. The technique stereo-DOV recorded a significant decrease in harvested individuals at both the assemblage and species level (primarily herbivorous species). The technique stereo-BRUV also recorded an impact at the assemblage level, but only for carnivorous fishes, which were less numerous in the catch. UVC did not detect an impact of the harvest at the assemblage or species level. We conclude that stereo-DOV is the most suitable technique for detecting the impacts of harvests and monitoring the effectiveness of PHCs as a fisheries management strategy, especially in areas where herbivorous fish are targeted. However, stereo-BRUV may be more appropriate where strong gradients in the abundance of carnivorous species or behavioural responses to divers are expected.

Resilient communities? Collapse and recovery of a social-ecological system in Arctic Norway

Broderstad, E. G., and E. Eythórsson. 2014. Resilient communities? Collapse and recovery of a social-ecological system in Arctic Norway. Ecology and Society 19(3): 1. https://doi.org/10.5751/ES-06533-190301

Marine biodiversity and sustainability of fishing resources in Brazil: a case study of the coast of Paraná state

The subtropical coastal zone of Paranastate in southern Brazil is only 80 km long yet environmentally diverse, with relatively pristine coastal landscapes and high marine and coastal biodiversity supporting important arti- sanal fishing grounds. However, this region began to change in the early 1970s. The development of industrial harbors, as well as unregulated tourism and urban settle- ment and pollution caused the loss of natural habitats. In addition, commercial shrimp trawlers began to operate in the adjacent shallow shelf areas. Biodiversity was seriously affected, and local fish stocks have decreased drastically in the last four decades. This article describes a long-term program to protect coastal habitats, recover marine biodi- versity and diversify the economic base of fishing com- munities in order to guarantee fish stocks for future generations, hence preserving the social and cultural identities of these communities. Although it is difficult to change traditional fishing practices, fishing communities may exploit alternate components of the marine biological resources in order to achieve environmental, social and cultural sustainability in the long term.

Near-ubiquity of ice-edge blooms in the Arctic

Abstract. Ice-edge blooms are significant features of Arctic primary production, yet have received relatively little attention. Here we combine satellite ocean colour and sea-ice data in a pan-Arctic study. Ice-edge blooms occur in all seasonally ice-covered areas and from spring to late summer, being observed in 77–89% of locations for which adequate data exist, and usually peaking within 20 days of ice retreat. They sometimes form long belts along the ice-edge (greater than 100 km), although smaller structures were also found. The bloom peak is on average more than 1 mg m−3, with major blooms more than 10 mg m−3, and is usually located close to the ice-edge, though not always. Some propagate behind the receding ice-edge over hundreds of kilometres and over several months, while others remain stationary. The strong connection between ice retreat and productivity suggests that the ongoing changes in Arctic sea-ice may have a significant impact on higher trophic levels and local fish stocks.