Brandt's cormorant diet (1994–2012) indicates the importance of fall ocean conditions for northern anchovy in central California

Effective ecosystem‐based management requires a comprehensive understanding of the functional links in the system. In many marine systems, forage species constitute a critical link between primary production and upper trophic level marine predators. As top predators, seabirds can be indicators of the forage species they consume and the ocean processes that influence these populations. We analyzed the diet and breeding success for the years 1994, 2003, 2005, and 2007–2012 of the Brandt's cormorant (Phalacrocorax penicillatus), a piscivorous diving seabird, breeding in central California, to evaluate the extent to which cormorant diet composition relates to prey availability, and how diet composition relates to breeding success and ocean conditions. Cormorant diet was primarily composed of young‐of‐the‐year (YOY) northern anchovy (Engraulis mordax), YOY rockfish (Sebastes spp.), and several species of small flatfish (order Pleuronectiformes). YOY rockfish consumption was positively related to their abundance as measured in a late spring pelagic midwater trawl survey. Northern anchovy appeared to be the most important prey as its consumption was positively related to cormorant breeding success. More northern anchovy were consumed in years where warm‐water conditions prevailed in the fall season before cormorant breeding. Thus, warm ocean conditions in the fall appear to be an important contributing factor in producing a strong year‐class of northern anchovy in central California and consequently a strong‐year class of Brandt's cormorant on the Farallon Islands.     

Are bycatch rates sufficient as the principal fishery performance measure and method of assessment for seabirds?

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Tori‐lines with weighted branch lines reduce seabird bycatch in eastern South Pacific longline fishery

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Integrated management to address the incidental mortality of seabirds in longline fisheries

1. Of the myriad of anthropogenic and natural threats to seabirds, one of the most critical global problems is incidental mortality in longline fisheries. Hesitance or failure by fishery managers and longline industries to adequately address this acute problem could result in the extinction of several albatross and petrel species within our lifetimes. 2. An integrated management approach is needed to comprehensively manage longline fisheries to address seabird bycatch. A review of relevant multilateral accords, declarations and actions by regional and international organizations reveals the need to augment international collaboration, especially to address pirate longline fishing. Management authorities and stakeholders need to collaborate to: promote adoption and compliance with effective legally binding accords that cover the ranges of all affected seabirds; ensure that all Range States and relevant distant water fishing nations become contracting parties to these accords; coordinate national implementation of the Food and Agriculture Organization's International Plan of Action on seabirds; set management goals; establish and implement policies to employ seabird deterrent measures; disseminate information on new deterrent measures; locally tailor seabird deterrent measures; standardize data reporting and establish a centralized data repository; coordinate research and monitoring; develop regional surveillance and enforcement systems; and augment less developed countries' capacity and resources to mitigate seabird and longline fishery interactions. 3. Establishing protected areas containing seabird colonies and adjacent waters within a nation's Exclusive Economic Zone (EEZ) is potentially an expedient method to reduce interactions between seabirds and longline fisheries. However, establishing high seas marine protected areas to restrict longline fishing in seabird foraging areas, which would require extensive and dynamic boundaries and large buffer zones, may not be a viable short‐term solution due to the long time it is anticipated it could take to resolve legal complications with international treaties, to achieve international consensus and political will, and to acquire requisite extensive resources for surveillance and enforcement. High seas marine protected areas may eventually become a feasible mechanism to address seabird bycatch if nations develop the will to close ocean areas to commercial fisheries to attempt to rehabilitate depleted pelagic fish stocks. 4. Direct involvement of longline industries, through partnerships with national governments and regional organizations, to develop seabird mitigation measures and policies prescribing the use of these measures, is critical. Direct involvement of stakeholders to find solutions to resource management problems leads to stakeholder groups taking ownership of and supporting rules. Bottom‐up approaches are successful in changing interest groups' attitudes and behaviour, to maximize voluntary compliance and minimize conflict and resources required for enforcement. 5. Data gaps must be filled and scientific uncertainty addressed through multilateral collaboration. Research to develop and improve practicable mitigation measures is most urgently needed. Information on the status and trends of albatross populations, where albatrosses forage, the causes of population declines, seabird mortality rates and levels in each longline fishery, and the type of impacts from longlining on seabird populations is also needed. It is well documented that several seabird species are at risk of extinction, incidental bycatch in longline fisheries significantly contributes to many species' decline, and proven mitigation measures are available. Thus, while additional research is critically needed, we should not delay taking precautionary action to wait for additional information, but should immediately act to protect seabirds from the known acute threat of mortality in longline fisheries. Copyright © 2001 John Wiley & Sons, Ltd.     

Clupeoid larval growth and plankton production in the Benguela upwelling system

Upwelling is a characteristic feature of the Benguela system. Strong upwelling leads to high primary production, which, in turn, supports large biomass of higher trophic levels. To analyse intra‐, interannual and decadal variability of fish recruitment, growth, and distribution, different methods to quantify this upwelling have been used. In the present work, an upwelling index, modelled diatom primary production, based on outputs from a numerical model for the Benguela upwelling system, is proposed. Upwelled water brings large amounts of nutrients into the euphotic zone and this supports primary productivity, which can be considered a preconditioner for the zooplankton that clupeoid larvae feed on. Therefore, it is assumed that high upwelling gives the potential for good feeding conditions for these larvae. This fact has motivated the use of the modelled index for upwelling intensity as a proxy for food availability and an investigation of the interannual variability of observed mean individual weight of Cape anchovy (Engraulis capensis) and sardine (Sardinops sagax) recruits. The study shows that the mean Cape anchovy recruit weight has a linear relationship with upwelling activity along the transport route (from the spawning to the nursery areas) and inside the nursery areas, while sardine have an Optimal Environmental Window (OEW) relationship to the upwelling on the transport route. A possible explanation for these observed differences is the prey the larvae feed on and the change in the plankton community as a function of upwelling activity.     

Seabird bycatch vulnerability to pelagic longline fisheries: Ecological traits matter

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Effect of ENSO on the distribution and concentration of catches and reproductive activity of anchovy Engraulis ringens in northern Chile

Anchovy makes up 90% of pelagic fishery catches in northern Chile. For the present work, anchovy (Engraulis ringens, Jenyns 1842) catches between 1997 and 2016 were analyzed to determine changes in distribution, concentration, and reproductive behavior before, during, and after ENSO events, using spatial indexes: gravity center (GC), inertia, coverage (CI), Gini index, and gonadosomatic index (GI). At the start of ENSO, anchovy catches increased and concentrated along the coast (rising Gini index), while CI decreased. During ENSO, Gini decreased, registering a southward displacement of the GC and smaller catches. In the long run, anchovy occupied lesser area (<CI) starting from 2008, concentrating in coastal areas. It developed a size structure composed mainly of specimens smaller than 17.0 cm. In addition, specimens < 12.0 cm were positively correlated with thermal anomalies, CI and MEI, reaching more than 60% of the catches during the 1997–1998 and 2015–2016 ENSO cycles. Results suggest that the warm phase of ENSO alters the anchovies’ reproductive activity, delaying its onset up to 4 weeks, and reducing GI intensity to 50%, due to increased participation in the reproductive process of individuals 12.0–13.5 cm. Therefore, large‐scale environmental processes, such as ENSO, significantly affect size structure and contribute to reduction of occupied area and higher reproductive activity of small‐size anchovies.     

Seabird interactions and by‐catch in the anchovy pelagic trawl fishery operating in northern Argentina

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Seasonal and interannual variations of oceanographic conditions off Mangalore coast (Karnataka, India) in the Malabar upwelling system during 1995–2004 and their influences on the pelagic fishery

Mangalore coast is well known for its multi‐species and multi‐gear fisheries and the fishery and oceanographic features of this region is a true representation of the Malabar upwelling system. Ten years of study (1995–2004) of oceanographic parameters has been carried out from the inshore waters off Mangalore to understand their seasonal and interannual variations and influences on the pelagic fishery of the region. Attempt has been also made to understand the influence of local and global environmental conditions on the alternating patterns of abundance between the Indian mackerel and oil sardine from the area. Field‐ and satellite‐derived oceanographic data have shown that coastal upwelling occurs during July–September with a peak in August resulting in high nutrient concentrations and biological productivity along the coast. Nearly 70% of the pelagic fish catch, dominated by oil sardine and mackerel, was obtained during September–December, during or immediately after the upwelling season. Catches of scombroid fishes were significantly related to cold Sea Surface Temperature, while such relationships were not observed for sardines and anchovies. Significant positive correlations were observed between the ENSO events (MEI) and seawater temperature from the study area. The extreme oceanographic events associated with the cold La Niña, which preceded the exceptional 1997–98 El Niño event, were responsible for the collapse of the pelagic fishery, especially the mackerel fishery along the southwest coast of India (Malabar upwelling system). Coinciding with the collapse of the mackerel fishery, oil sardine populations revived during 1999–2000 all along the southwest coast of India. Tolerance of oil sardine to El Niño / La Niña events and the low predatory pressure experienced by their eggs and larvae due to the collapse of mackerel population might have resulted in its population revival.     

Seabird‐trawling interactions: factors affecting species‐specific to regional community utilisation of fisheries waste

Bottom trawl fishing provides substantial amounts of normally unavailable demersal prey to seabirds (e.g., discards), affecting their life‐history traits and population dynamics, as well as community structure. Within this framework, we studied seabird‐trawling interactions throughout the annual cycle in a poorly studied ecosystem in the Mediterranean, the Balearic archipelago, on a both species‐specific and a community level. Whereas the species‐specific approach showed a significant influence of season (phenology) on shaping seabird’s trawling attendance patterns, the spatio‐temporal coupling of regional community was a result of a complex interaction between fishery‐related variables. The most frequent and abundant species were the yellow‐legged gull Larus michahellis and Cory’s shearwater Calonectris diomedea, the latter attending vessels in higher numbers than expected from local population figures. Conversely, the remaining breeding species occurred in lower numbers than expected according to their local breeding populations, suggesting that discards were of relatively little importance. Discarding activity took place over the entire shelf and continental slope surrounding Mallorca, but especially in the southwest, adjacent to the breeding grounds of approximately 12% of the Balearic total seabird breeding population, including 13% the Balearic shearwater Puffinus mauretanicus world population. Overall discards corresponded to 0.74 of landings (range: 0.09–6.00) and consisted primarily of fish followed by crustaceans and molluscs (approximately 80, 15, and 5%, respectively). Seabird‐trawling interactions should be taken into account in the frame of an ecosystem‐based approach to fisheries management, and particular attention should be devoted to the critically endangered Balearic shearwater.     

Climate,oceanography, and recruitment: the case of the Bay of Biscay anchovy (Engraulis encrasicolus)

The Bay of Biscay anchovy has experienced, since 2001, a succession of low recruitments, resulting in the collapse of the stock in 2005; this has led to successive closures of the fishery. This study investigates the possible impact of different controlling factors [North Atlantic Oscillation (NAO), East Atlantic (EA) pattern, turbulence, upwelling, and river flow] upon anchovy recruitment and fishery catches. Fifty‐five percent of the recruitment variability of this fishery can be explained by upwelling over the spawning area; this is related, in turn, to the EA pattern. The conceptual understanding of the system proposed for the Bay of Biscay anchovy suggests that negative EA periods are associated with northeasterly wind circulation, which produces weak upwelling over the continental shelf. This pattern results in hydrodynamic stability over the area, leading, probably, to adequate food availability. A positive EA (which extends onwards, from 1998) is associated with southwesterly winds and downwelling over the continental shelf; this leads, probably, to the dispersion of anchovy food and larvae, together with increasing mortality.     

Anchovy (Engraulis ringens) and sardine (Sardinops sagax) spatial dynamics and aggregation patterns in the Humboldt Current ecosystem, Peru, from 1983–2003

Three indexes of spatial aggregation are developed and used to examine the aggregation pattern of sardine (Sardinops sagax) and anchovy (Engraulis ringens) in the Peruvian Humboldt Current System, determined from 36 acoustic surveys conducted from 1983 through 2003 by the Peruvian Marine Institute (IMARPE). Each index assesses a different aspect of aggregation: the concentration, the percent occupancy of space and the clustering of high‐fish abundance. Both time‐series correlation and tree‐based clustering‐regression method, classification and regression trees (CART), were used to relate each of the indexes to environmental variables (season, temperature anomaly and year). Additionally, a measure of onshore–offshore distribution, the average distance from the coast, and abundance variables (the average acoustic backscatter per occupied sampling unit, and the acoustically estimated total abundance of sardine and anchovy from IMARPE) were related to environmental factors by using CART. We show that the 1983–2003 time series can be divided into three different periods: with shifts in 1992 and in 1997–98. Sardine and anchovy showed large differences in both abundance and aggregation among these periods. Although upwelling ecosystems support dramatic and sudden changes in environmental conditions, fish responses are sometimes smoother than usually suggested and there are transition periods with concomitant high biomasses of anchovy and sardine, but with different spatial aggregation patterns. Observed relationships between environmental proxies and aggregation patterns support the habitat‐based hypothesis that environmentally mediated alterations in range lead to population changes.     

A selective and low impacting traditional fishery,sustaining the economy of small coastal villages in central Mediterranean: Keep or replace the small‐scale driftnets?

Small‐scale driftnets (SSDs) have been historically used in the Mediterranean without major environmental concern. The introduction of large‐scale driftnets caused unwanted catches of protected species. Specific regulations were therefore issued in European waters, culminating in a proposed moratorium on SSDs. This study aimed to characterise the SSD fishery targeting anchovy (menaide), evaluating its environmental sustainability, economic performance and social relevance. In 2013, a survey by interviews, logbooks and observers on board assessed the order of magnitude of this fishery in terms of fishing capacity and activity, volume of landings and revenues. The menaide fleet consisted in 60 vessels <12 m overall length, moored in little harbours in southern Italy. These nets are highly selective: the target species, European anchovy, Engraulis encrasicholus (L.) and sardine, Sardina pilchardus (Walbaum), dominates the catches, while discards are negligible. The anchovies caught are of high quality and large size; the high prices support fish processing by local factories. Moreover, the results of a SWOT analysis demonstrated that replacing SSDs with a semi‐industrial fishery, like purse seining, would increase impacts on the ecosystem, and a loss of socio‐economic opportunities for several coastal villages. These findings support the option of keeping SSDs operating, in the framework of specifically oriented management measures.     

Application of high‐throughput single nucleotide polymorphism genotyping for assessing the origin of Engraulis encrasicolus eggs

1. Single nucleotide polymorphism (SNP) markers in anchovy (Engraulis encrasicolus) egg samples were analysed to detect their origin on a small spatial scale (200 km) by assigning genotypes to adult anchovy stocks. The novelty of this work is the application of a rapid high‐throughput method for genotyping each single anchovy egg, in a single execution, using a set of 96 genome‐wide SNPs in a dynamic array system with microfluidic technology (Fluidigm 96.96).
2. The existence of two ecotypes in E. encrasicolus had already been identified based on SNP polymorphism in the Atlantic Ocean and in the Mediterranean Sea, showing that habitat type (offshore versus coastal/estuarine) is the most important component of genetic differentiation among populations of anchovy.
3. In this work, anchovy egg genotypes from areas of the Western Mediterranean were assigned to adult populations. Only two localities in which adult anchovies were sampled represented donor populations for the coastal/estuarine egg genotypes. Although some degree of mixing among the hauls could exist, the assignment of egg groups to adult populations led to distinguishing the contributions of distinct ecotypes to new wild generations. We can conclude that the high rate of egg dispersion caused by marine currents and the different degrees of local retention could explain the genetic heterogeneity observed in the adult populations, where eggs from neighbouring spawning sites tend to mix.
4. The results highlight that this technique represents a new and useful tool for addressing evolutionary questions, breed recognition, assignment, and connectivity assessment of individual eggs, and anchovy population dynamics, for the management of stocks.

     

Characterization of seabird bycatch in eastern Canadian waters, 1998–2011, assessed from onboard fisheries observer data

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Scavenger communities and fisheries waste: North Sea discards support 3 million seabirds, 2 million fewer than in 1990

Every year fisheries discard >10 million tonnes of fish. This provides a bounty for scavengers, yet the ecological impact of discarding is understudied. Seabirds are the best‐studied discard scavengers and fisheries have shaped their movement ecology, demography and community structure. However, we know little about the number of scavenging seabirds that discards support, how this varies over time or might change as stocks and policy change. Here, we use a Bayesian bioenergetics model to estimate the number of scavenging birds potentially supported by discards in the North Sea (one of the highest discard‐producing regions) in 1990, around the peak of production, and again after discard declines in 2010. We estimate that North Sea discards declined by 48% from 509,840 tonnes in 1990 to 267,549 tonnes in 2010. This waste had the potential to support 5.66 (95% credible intervals: 3.33–9.74) million seabirds in the 1990s, declining by 39% to 3.45 (1.98–5.78) million birds by 2010. Our study reveals the potential for fishery discards to support very large scavenging seabird communities but also shows how this has declined over recent decades. Discard bans, like the European Union's Landing Obligation, may reduce inflated scavenger communities, but come against a backdrop of gradual declines potentially buffering deleterious impacts. More work is required to reduce uncertainty and to generate global estimates, but our study highlights the magnitude of scavenger communities potentially supported by discards and thus the importance of understanding the wider ecological consequences of dumping fisheries waste.     

Comprehensive estimates of seabird–fishery interactions for the US Northeast and mid‐Atlantic

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Predicting the current and future suitable habitat distributions of the anchovy (Engraulis ringens) using the Maxent model in the coastal areas off central‐northern Chile

An assessment of climate change impacts on the habitat suitability of fish species is an important tool to improve the understanding and decision‐making needed to reduce potential climate change effects based on the observed relationships of biological responses and environmental conditions. In this study, we use historical (2010–2015) environmental sea surface temperature (SST), upwelling index (UI), chlorophyll‐a (Chl‐a) and biological (i.e., anchovy adults acoustic presence) data (i.e., Maxent) to determine anchovy habitat suitability in the coastal areas off central‐northern (25°S–32°S) Chile. Using geographic information systems (GIS), the model was forced by changes in regionalized SST, UI and Chl‐a as projected by IPCC models under the RPC (i.e., RCP2.6, RCP4.5, RCP6.0 and RCP8.5) emissions scenarios for the simulation period 2015–2050. The model simulates, for all RCP scenarios, negative responses in anchovy presence, reflecting the predicted changes in environmental variables, dominated by a future positive (warming) change in SST and UI, and a decrease in chlorophyll‐a (i.e., phytoplankton biomass). The model predicts negative changes in habitat suitability in coastal areas from north of Taltal (25°S) to south of Caldera (27°45′S) and in Coquimbo littoral zone (29°–30°12′S). The habitat suitability models and climate change predictions identified in this study may provide a scientific basis for the development of management measures for anchovy fisheries in the coastal areas of the South American coast and other parts of the world.     

Hydrographic phenomena influencing early life stages of the Sicilian Channel anchovy

The information collected from a European Union funded project on the ‘Distribution Biology and Biomass Estimates of the Sicilian Channel Anchovy (Engraulis encrasicolus)’ was used to analyse the linkage between the general circulation pattern of the Atlantic Ionian Stream (AIS) and the reproductive strategy of the Sicilian Channel anchovy. The main spawning ground is located in the NW region of the southern Sicilian coast. This region is a stable area of low current produced by the impingement towards the coast of the AIS and its bifurcation into two branches. The main branch heads towards the SE end of the Sicilian coast (Cape Passero) acting as a transport mechanism for the anchovy eggs and larvae. Along the AIS trajectory, there is a density front to the left of the current, facing downstream. This front is a consequence of the shoreward sloping of isopycnals that maintains the geostrophic flow, facilitating the mixing of deeper waters with surface layers and fertilization of coastal waters. The front enhances primary production assuring food availability for anchovy larvae during their advection by the AIS. The highest concentrations of larval anchovy were found off the SE Sicilian coast, in the area off Cape Passero. The greater average sizes of larvae found in this region, and their estimated age, support the evidence of advection by the AIS. The hydrographic features observed in this area, such as the existence of a well‐defined cyclonic vortex, implies the existence of upwelling in its centre, providing a suitable environment for sustained enhanced rates of primary production and allowing the larval population to maintain their relative position. This retention area is conceived as favourable for providing the necessary feeding conditions. The data acquired from a survey carried out to evaluate the anchovy recruitment strength confirm that larvae reach the juvenile stage in the south‐eastern coast of Sicily, since most of the young‐of‐the‐year anchovy were located in the Cape Passero region.     

Bonga shad (Ethmalosa fimbriata) spawning tactics in an upwelling environment

Successful recruitment in small pelagic fish populations inhabiting upwelling zones is subject to variation in fecundity and is driven by spatial and temporal fluctuations in environmental conditions, that is, mainly sea surface temperature, salinity and food availability. These fluctuations in abiotic factors have stimulated small pelagic fish populations to exhibit specifically adapted spawning tactics. To better understand to what extent a short‐lived exploited fish species such as bonga shad Ethmalosa fimbriata has adapted to an upwelling environment, we have investigated the interrelationship between upwelling intensity as a proxy for productivity and population fecundity by means of a virtual population analysis. We found that females of intermediate size contributed significantly more eggs to the population's fecundity than smaller or larger ones. Our model results further indicate that E. fimbriata exhibits a spawning preference at water temperatures of around 25°C and upwelling intensities of around 2.5 m³ s^?1 m^?1. Hence, we hypothesize that climate change‐driven increases in sea temperatures and modifications of upwelling‐favourable winds could significantly impact the species’ reproductive biology. To understand how climate change might impact fisheries, spawning tactics of small pelagic fishes are important to assess as well as their recruitment success. Such information is particularly relevant in countries where the fishery is critical at socio‐economic level, to better implement fisheries management addressing multiple stressors.