The Ecuadorian Artisanal Fishery for Large Pelagics: Species Composition and Spatio-Temporal Dynamics

The artisanal fisheries of Ecuador operate within one of the most dynamic and productive marine ecosystems of the world. This study investigates the catch composition of the Ecuadorian artisanal fishery for large pelagic fishes, including aspects of its spatio-temporal dynamics. The analyses of this study are based on the most extensive dataset available to date for this fishery: a total of 106,963 trip-landing inspection records collected at its five principal ports during 2008 ‒ 2012. Ecuadorian artisanal fisheries remove a substantial amount of biomass from the upper trophic-level predatory fish community of the eastern tropical Pacific Ocean. It is estimated that at least 135 thousand metric tons (mt) (about 15.5 million fish) were landed in the five principal ports during the study period. The great novelty of Ecuadorian artisanal fisheries is the “oceanic-artisanal” fleet component, which consists of mother-ship (nodriza) boats with their towed fiber-glass skiffs (fibras) operating with pelagic longlines. This fleet has fully expanded into oceanic waters as far offshore as 100°W, west of the Galapagos Archipelago. It is estimated that nodriza operations produce as much as 80% of the total catches of the artisanal fishery. The remainder is produced by independent fibras operating in inshore waters with pelagic longlines and/or surface gillnets. A multivariate regression tree analysis was used to investigate spatio-environmental effects on the nodriza fleet (n = 6,821 trips). The catch species composition of the nodriza fleet is strongly influenced by the northwesterly circulation of the Humboldt Current along the coast of Peru and its associated cold waters masses. The target species and longline gear-type used by nodrizas change seasonally with the incursion of cool waters (< 25°C) from the south and offshore. During this season, dolphinfish (Coryphaena hippurus) dominates the catches. However, in warmer waters, the fishery changes to tuna-billfish-shark longline gear and the catch composition becomes much more diverse.     

Quantifying the effects of fisheries on threatened species: the impact of pelagic longlines on loggerhead and leatherback sea turtles

The depletion of fish stocks from global fisheries has been a long‐standing concern. More recently, incidental catch of non‐target (termed bycatch) vertebrates also has been proposed as a serious conservation issue. Here we present a bycatch assessment for loggerhead and leatherback sea turtles that are incidentally caught by global pelagic longlines. We integrate catch data from over 40 nations and bycatch data from 13 international observer programmes. Despite infrequent rates of encounter, our analyses show that more than 200 000 loggerheads and 50 000 leatherbacks were likely taken as pelagic longline bycatch in 2000. Our analyses suggest that thousands of these turtles die each year from longline gear in the Pacific Ocean alone. Given 80–95% declines for Pacific loggerhead and leatherback populations over the last 20 years, this bycatch level is not sustainable. Adopting a large‐scale, synthetic approach is critical to accurately characterize the influence of global fisheries bycatch on globally distributed and imperilled pelagic vertebrates.     

Features of species composition and abundance of the nekton community in the upper epipelagic layer of the Northwest Pacific in early summer

The composition and structure of nekton in the upper epipelagic zone is considered based on the data of trawl surveys conducted in the Northwestern Pacific Ocean and adjacent waters in 2004–2009. Alterations in the nekton community during the early summer period, as well as peculiarities of its species composition and quantitative distribution that depend on changes in background conditions are described. In total, as many as 66 species of fish and 22 species of cephalopods were recorded in catches for the studied period. The lowest biodiversity was found in the near-shore waters (areas nos. 5, 7, and 9) and the highest one was in open oceanic waters (area no. 13). In 2004–2009, nekton biomass was formed mainly by mesopelagic species and their share amounted to 40–60% of the entire nekton community. Pacific salmon varied within 17–37% the total nekton biomass in various years. In general, for the period of studies, the mean biomass of nekton community was 2 431 000 tons, and in 2009, the total biomass approached this value.     

Intra and interspecific association of large pelagic fishes inferred from catch data of surface longline

Synopsis This paper analyses the distribution of longline catches of swordfish, Xiphias gladius, and six species of pelagic elasmobranchs, during a fishing voyage in the tropical eastern Atlantic. Seven scales of sampling units, ranging from about 0.72 to 7.2 km were used. Observed frequencies of appearance of each species in the basic sampling unit, were compared with theoretical frequencies obtained from the Poisson and negative binomial distributions. For the study of the interspecific relationships, contingency tables were used and the degree of association was estimated using the ²test and the coefficient v of Kendall. The catch distribution of the swordfish and the devil ray (Mobula sp.) can be explained by both randomness and a slight trend to association. For the pelagic sharks, a clear trend towards intraspecific clustering was found. Catches of two species of the genus Carcharhinus showed the most positive trends to interspecific association, especially in short ranges, probably due to attraction to previously hooked fish. The possible causes of these distributions are discussed.     

Reconstruction of coral reef fisheries catches in American Samoa, 1950–2002

Fisheries catches from Pacific Island coral reefs are rarely recorded in official statistics. Reconstruction of catch estimates with limited hard data requires interpolation and assumptions, justifiable only by the unsatisfactory alternative of continued substitution of zero catches, a common policy interpretation for ‘no data’. Uncertainties associated with reconstructions are high, requiring conservative estimation. American Samoan domestic fisheries consist of an artisanal, small-boat sector, whose commercial catches are reported, and a shore-based subsistence sector, with no regular reporting. Our catch reconstruction (with large pelagic species removed) suggested a 79% decrease in catches between 1950 (752 t) and 2002 (155 t). Accounting for rapid human population growth on the main island, the per capita catch rate may have declined from 36.3 kg·person⁻¹ year⁻¹ in 1950 to 1.3 kg·person⁻¹ year⁻¹ by 2002, while the catch rate for the inhabited outer islands has been independently reported as 58.6 kg·person⁻¹ year⁻¹. Catch per area of coral reef (to 50-m depth) may have declined from 5.5 to 0.7 t km⁻² year⁻¹ for the main island, and from 9.1 to 4.9 t km⁻² year⁻¹ for the outer islands, for 1950 and 2002, respectively. Summed for 1950–2002, our reconstruction suggested a 17-fold difference between reconstructed estimates and reported statistics.     

Spatial distribution and features of biology of Pacific sleeper shark Somniosus pacificus in the North Pacific

The results of the investigations of spatial and vertical distribution of Pacific sleeper shark Somniosus pacificus in the North Pacific Ocean conducted for many years are presented. In addition, the size distribution and features of biology of the species are studied. The largest abundance of the species is registered in the Bering Sea, western Gulf of Alaska, eastern Aleutian Islands, and Pacific waters of northern Kuril Islands and southeastern Kamchatka. The species is the most abundant near the bottom at the depth from 200 to 700 m and in the pelagic waters at a depth of 100–200 m. The average depths of the catches of Pacific sleeper shark substantially change over the year reaching minimum values in June and maximum values in December. Vertical daily migrations (to the water column at night and to the bottom during the day) are registered. The catches are represented by fish 26–352 cm in length, and sharks 100–200 cm in length prevail. The males are noticeably smaller than the females. In general, condition of the fishes decreases and feeding intensity increases with growth. Food composition substantially changes with the increase of body length: consumption of squids decreases and consumption of crustaceans, fishes, and fishery wastes increases. The food composition is slightly different in the females and males.     

Ecological role and historical trends of large pelagic predators in a subtropical marine ecosystem of the South Atlantic

Large pelagic predators occupy high positions in food webs and could control lower trophic level species by direct and indirect ecological interactions. In this study we aimed to test the hypotheses: (1) pelagic predators are keystone species, and their removals could trigger impacts on the food chain; (2) higher landings of pelagic predators could trigger fishing impacts with time leading to a drop in the mean trophic level of catches; and (3) recovery in the pelagic predators populations, especially for sharks, could be achieved with fishing effort reduction. We performed a food web approach using an Ecopath with Ecosim model to represent the Southeastern and Southern Brazil, a subtropical marine ecosystem, in 2001. We then calibrated the baseline model using catch and fishing effort time series from 2001 to 2012. Afterwards, we simulated the impact of fishing effort changes on species and assessed the ecological impacts on the pelagic community from 2012 to 2025. Results showed that the model was well fitted to landing data for the majority of groups. The pelagic predators species were classified as keystone species impacting mainly on pelagic community. The ecosystem was resilient and fisheries seem sustainable at that time. However, the temporal simulation, from 2001 to 2012, revealed declines in the biomass of three sharks, tuna and billfish groups. It was possible observe declines in the mean trophic level of the catch and in the mean total length of landings. Longline fisheries particularly affected the sharks, billfish and swordfish, while hammerhead sharks were mostly impacted by gillnet fishery. Model simulations showed that large sharks’ biomasses could be recovered or maintained only after strong fishing effort reduction.     

Specific features of distribution and ecology of Lycenchelys fedorovi (Zoarcidae) in Pacific waters off the northern Kuril Islands

On the basis of material for 1993–2002, data are provided on occurrence, spatial-bathymetric distribution, and size composition of Lycenchelys fedorovi, as well as on species that occur simultaneously with it in catches in Pacific waters off the northern Kuril Islands. This relatively scarce, medium-sized representative of the family Zoarcidae (maximum length of 42 cm, body weight 200 g) during the period of studies occurred only at the site to the south of the Fourth Kuril Strait in the range of depths 220–775 m at the near-bottom temperature of 1.6–4.2°C. The dependence between the depth of catch and sizes of L. fedorovi was analyzed. It was shown that the size of its catches in Pacific waters off the northern Kuril Islands is subjected to some interannual, seasonal, and diurnal dynamics.     

Changes in experimental gillnet catches from the Kafue Floodplain, Zambia, since construction of the Kafue Gorge Dam

The Kafue Floodplain fishery produces an annual fish yield of about 5000 tonnes. The 1971 closure of the Kafue Gorge Dam downstream from the floodplain modified flooding patterns. Pre-impoundment studies predicted this modification would increase fish stocks. Experimental gillnets set in 1975 and 1976 caught 18 species on a regular basis, nine of which were abundant enough for comparison with catches in similar gillnet samples taken prior to completion of the Kafue Gorge Dam. Of these nine species, experimental gillnet catches of three predator species were smaller in 1975–76 than in 1969–70. Catches of only one species increased significantly. Whether this change is due to the modified flooding pattern is unclear; unusually dry flood conditions in 1973 and increased fishing effort may have contributed.     

Biological features of the common fish species in Olyutorsky-Navarin region and the adjacent waters of the Bering Sea: 1. Gadidae (cods) family

Biological features of the three common fish species, pollock Theragra chalcogramma, Pacific cod Gadus macrocephalus, and saffron cod Eleginus gracilis (Gadidae), have been studied using a 20-year dataset (1995?2015). These species inhabit the northwestern Bering Sea in the summer–autumn period and form the schoolings in Olyutorsky-Navarin region. The size–age parameters, as well as the peculiarities of the body length and body weight dynamics, spawning periods, spawning range, and conditions, of the fish caught by different sampling gear have been analyzed. Due to the construction peculiarities and catch efficiency of the different catching gear, the largest specimens are found in the setlines and snurrevads; the fish caught by the trawls are characterized by the smallest size. The body length and body weight of pollock is greater in the pelagic trawl catches compared to the bottom trawl catches. The abundant brood of Gadidae may well be tracked on the multiyear dynamics graphs reflecting the size distribution, as well as by the decrease of biological parameters of the fish. The studied species inhabit the vast growth areas, so smaller body size of them in the coastal waters may be a result of a high ratio of the young specimens there.     

Decline of the African lungfish (Protopterus aethiopicus) in Lake Victoria (East Africa)

Catch and effort data for the period 1973–1990 demonstrate a dramatic decline of lungfish in the Tanzanian waters of Lake Victoria. Bottom trawl catches in the Mwanza Gulf showed a decline in catch rates from 67.5 kg h⁻¹ in 1973 to 5.5 kg h⁻¹ in 1986. Trawling of commercial vessels in the Speke Gulf revealed a decline in lungfish catches from 1.3 kg h⁻¹ in 1986 to 0.07 kg h⁻¹ in 1990. The development of anoxia in the deeper waters of Lake Victoria, the algal blooms, and the decline of water transparency, all associated with eutrophication, are not likely to have contributed to the decreased catch rate. However, the lungfish decline may reflect the interaction of overexploitation by the fishery and a low level of Nile perch predation that restricts lungfish to wetland refugia. We suggest that this may have been reinforced over the past few decades by large-scale conversion of wetlands to agricultural land and harvesting of nest-guarding male lungfish leading to decreased recruitment of young.     

Specific features of distribution and ecology of sawback poacher Sarritor frenatus (Agonidae) in Pacific Waters of the Northern Kuril Islands and Southeast Kamchatka

According to materials of 1992–2002, data on the occurrence, spatial-bathymetric distribution, and size-weight composition of sawback poacher Sarritor frenatus and species accompanying it in catches in Pacific waters of the northern Kuril Islands and southeastern Kamchatka are provided. This comparatively numerous and relatively small representative of the family Agonidae (maximum length 31 cm, body weight 103 g) in the period of studies was found uniformly at depths of 78-790 m at near-bottom temperature of ?1.2 to ?4.2°C. In spring, summer, and winter months, maximum catches (over 500–1000 ind./h of trawling) were recorded in the southernmost and northernmost sites of the study area in a bathymetric range of 101–500 m; increased concentrations of this poacher were recorded also on the beam of the Fourth Kuril Strait near the southeastern extremity of Paramushir Island only in the autumn period. The ratio between the depth of catch and the sizes of sawback poacher is analyzed, and the data on the composition of its food in waters of the northern Kuril Islands is given. It is shown that the occurrence and amount of catches of this poacher in Pacific waters of the northern Kuril Islands and southeastern Kamchatka are subjected to some interannual, seasonal, and diurnal dynamics.     

Biomass and Abundance Biases in European Standard Gillnet Sampling

The European Standard EN 14757 recommends gillnet mesh sizes that range from 5 to 55mm (knot-to-knot) for the standard monitoring of fish assemblages and suggests adding gillnets with larger mesh sizes if necessary. Our research showed that the recommended range of mesh sizes did not provide a representative picture of fish sizes for larger species that commonly occur in continental Europe. We developed a novel, large mesh gillnet which consists of mesh sizes 70, 90, 110 and 135mm (knot to knot, 10m panels) and assessed its added value for monitoring purposes. From selectivity curves obtained by sampling with single mesh size gillnets (11 mesh sizes 6 – 55mm) and large mesh gillnets, we identified the threshold length of bream (Abramis brama) above which this widespread large species was underestimated by European standard gillnet catches. We tested the European Standard gillnet by comparing its size composition with that obtained during concurrent pelagic trawling and purse seining in a cyprinid-dominated reservoir and found that the European Standard underestimated fish larger than 292mm by 26 times. The inclusion of large mesh gillnets in the sampling design removed this underestimation. We analysed the length-age relationship of bream in the Římov Reservoir, and concluded that catches of bream larger than 292mm and older than five years were seriously underrepresented in European Standard gillnet catches. The Římov Reservoir is a typical cyprinid-dominated water body where the biomass of bream > 292mm formed 70% of the pelagic trawl and purse seine catch. The species-specific relationships between the large mesh gillnet catch and European Standard catch suggested that the presence of carp (Cyprinus carpio), European catfish (Silurus glanis), tench (Tinca tinca) or bream warrants the use of both gillnet types. We suggest extending the gillnet series in the European Standard to avoid misinterpretation of fish community biomass estimates.     

Specific features of distribution and ecology of two species of sea poachers of genus Podothecus (Agonidae) in pacific waters off the northern Kuril Islands and southeastern Kamchatka

According to materials of studies in 1992–2002, data on occurrence, spatial-bathymetric distribution, and size-weight composition of two species of sea poachers of the genus Podothecus (P. accipenserinus and P. sturioides) and species accompanying them in catches in Pacific waters off the northern Kuril Islands and southeastern Kamchatka are provided. The distribution of these relatively large representatives of the family Agonidae (maximum length of the first species is 38 and that of the second species is 33 cm, body weight of both 200 g) noticeably differ. In the period of observations, P. accipenserinus was found in catches only to the north of the Fourth Kuril Strait at depths of 80–570 m at near-bottom temperature of ?0.70 to +4.25°C, while P. sturioides was found over the entire studied area in a wider bathymetric range (85–786 m) exclusively at positive values of near-bottom water temperature (0.10–3.55°C). However, more frequently and in greater amounts, both species of sea poachers were recorded in catches off the southeastern extremity of Kamchatka and from the oceanic side of the Shumshu and Paramushir islands. The relationship between the depth of catch and sizes of P. accipenserinus and P. sturioides was analyzed. It is shown that their occurrence and the magnitude of catches in Pacific waters off the northern Kuril Islands and southeastern Kamchatka are subjected to some interannual, seasonal, and diurnal dynamics.     

The fisheries biology of flying fishes (Families: Exocoetidae and Hemiramphidae) from the Camotes Sea, Central Philippines

The catches of a small artisanal fishery for flying fishes (Families Exocoetidae and Hemiramphidae) on the Danajon Bank in the Camotes Sea. Central Visayas, were recorded during a 14-month period between 1987–1988. Catches were made using floating drive-in-nets deployed from small motorized canoes. Three species, Cheilopogon nigricans, Cypselurus opisthopus and Oxyporhamphus convexus , formed about 90% of landings. Growth, mortality and related parameters for the three dominant species in the catch were estimated from length-frequency data. Seasonal variations in catch rate and recruitment are described and thought to be linked to the two monsoon periods in the Philippines. Total mortality rates were very high and, while these may be the result of migratory movements rather than attrition, they are a cause for concern in such a highly selective fishery.     

Climate change is projected to reduce carrying capacity and redistribute species richness in North Pacific pelagic marine ecosystems

Climate change is expected to impact all aspects of marine ecosystems, including fisheries. Here, we use output from a suite of 11 earth system models to examine projected changes in two ecosystem‐defining variables: temperature and food availability. In particular, we examine projected changes in epipelagic temperature and, as a proxy for food availability, zooplankton density. We find that under RCP8.5, a high business‐as‐usual greenhouse gas scenario, increasing temperatures may alter the spatial distribution of tuna and billfish species richness across the North Pacific basin. Furthermore, warmer waters and declining zooplankton densities may act together to lower carrying capacity for commercially valuable fish by 2–5% per decade over the 21st century. These changes have the potential to significantly impact the magnitude, composition, and distribution of commercial fish catch across the pelagic North Pacific. Such changes will in turn ultimately impact commercial fisheries’ economic value. Fishery managers should anticipate these climate impacts to ensure sustainable fishery yields and livelihoods.     

What saved the whales? An economic analysis of 20th century whaling

Catches of whales show a historically cyclical pattern, with catches declining as stocks of the financially most attractive species fell, but expanding as substitute species were caught. Total combined catch peaked in the early 1960s and fell thereafter to the current regulated levels. While it is widely thought that international whaling agreements account for the current stable stock levels, economic analysis reveals that market forces leading to reduced catch were already in place well before the agreements took hold. To some extent, therefore, catches were destined to decline as whale products ceased to be commercially attractive on a large scale. Using econometric analysis, the paper shows the various forces at work: declining stocks, the rise of substitute products, internationally increasing environmentalism, and rising incomes. Of these forces, stock decreases, which resulted in high unit catch costs, and income growth, which reduced rather than increased demand, were the most important factors, with regulation following, rather than leading, catch changes.     

Biological features of the common fish species in Olyutorsky-Navarin region and the adjacent waters of the Bering Sea: 2. Families Macrouridae,Clupeidae, and Osmeridae

Biological features of the four common fish species, giant grenadier Albatrossia pectoralis (Macrouridae), Pacific herring Clupea pallasii (Clupeidae), Pacific rainbow smelt Osmerus mordax dentex, and Pacific capelin Mallotus villosus catervarius (Osmeridae), were studied under the 20-year dataset (1995?2015). These species inhabit the northwestern Bering Sea in the summer–autumn period and form the schoolings in the Olyutorsky-Navarin region. The size–age parameters of the fish caught by different sampling gear, as well as the peculiarities of the body length and body weight dynamics, spawning periods, spawning range, and conditions, were analyzed. The largest specimens of giant grenadier, Pacific herring, and Pacific rainbow smelt were observed in the catches performed by the bottom setline and the gill nets; the smallest fish were found in the trawl catches. The body length and body weight of Pacific herring were larger in the pelagic trawls compared to the bottom trawls; an opposite pattern was observed for the Pacific capelin. The abundant year-class in the species with short life cycle (capelin and herring) is well tracked on the longterm plots of the fish body size; this is accompanied by the decrease of their biological parameters. Herring stock covers large growing grounds; smaller body size was observed for the herring grazing in the coastal waters; young specimens dominate here.     

On the Persistence of Stereotypes Concerning the Marine Ecology of Pacific Salmon (<Emphasis Type="Italic">Oncorhynchus</Emphasis> spp.)

Some of the views on the marine ecology of Pacific salmon (Oncorhynchus spp.) that were popular in the second half of the 20th century are discussed critically: the absolutization of the influence of sea surface temperature on distribution of salmon and strength of their year classes, as well as the conclusions on the shortage of food (particularly in winter) and the fierce competition for food, the “suppression” of other salmon species and own adjacent broodline by pink salmon, the limited carrying capacity of the pelagic zone of subarctic ocean waters for salmon, the distortion of the structure of epipelagic communities in ecosystems of the North Pacific due to the large-scale stock enhancement of chum salmon, etc. Most of these ideas have not been confirmed by the data of long-term monitoring conducted in the form of complex marine expeditions by the Pacific Research Fisheries Center (TINRO Center) in the Far-Eastern Seas and adjacent North Pacific waters since the 1980s. The data show that Pacific salmon are ecologically very flexible species with a wider temperature range of habitat than was previously believed. Salmon are able to make considerable vertical migrations, easily crossing zones of sharp temperature gradient and different water masses. Having the wide feeding spectra and being dispersed (as non-schooling fish) when feeding in the sea and ocean, they successfully satisfy their dietary needs in vast areas even with relatively low concentrations of prey organisms (macroplankton and small nekton). The total biomass of all the Pacific salmon species in the North Pacific is not greater than 4–5 million t (including 1.5–2.0 million t in Russian waters), whereas the biomass of other common species of nekton is a few hundreds of millions of tons. Salmon account for 1.0–5.0% of the total amount of food consumed by nekton in the epipelagic layer of the western Bering Sea, 0.5–1.0% in the Sea of Okhotsk, less than 1% in the ocean waters off the Kuril Islands, and 5.0–15.0% in the ocean waters off East Kamchatka. Thus, the role of Pacific salmon in the trophic webs of subarctic waters is rather moderate. Therefore, neither pink nor chum salmon can be considered as the species responsible for the large reorganization in ecosystems and the population fluctuations in other common nekton species.     

Arctic fisheries catches in Russia, USA, and Canada: baselines for neglected ecosystems

The Amerasian Arctic, covering northern Siberia (Russia), Arctic Alaska (USA), and the Canadian Arctic, extends over seven coastal Large Marine Ecosystems and makes up the seasonally ice-free part of FAO Statistical Area 18 (Arctic Sea). Historically, the harsh climate has limited marine fisheries (here excluding marine mammal hunting) to small-scale operations conducted mainly in estuaries and river deltas. Most of the catches have traditionally not been reported to FAO, with the result that total catch estimated here from 1950 to 2006 is 75 times higher than the sum of the catches reported for FAO 18 (Arctic). Catches were reconstructed from data on fishing communities in Canada and Alaska, and from various government and non-government sources for Siberia. Based on national data supplied to FAO since 1950, catches have been reported as 12,700 t in toto (reported on behalf of the former Soviet Union). This compares with our reconstructed catches of over 950,000 t, i.e., 770,000, 89,000, and 94,000 t by Russia, USA, and Canada, respectively for the same time period. The reconstructed catch (mainly whitefishes in Siberia, various salmonids in Alaska, and Arctic char in Canada) was 24,100 t year⁻¹ in 1950, but declined to 10,200 t year⁻¹ by the mid-2000s. Reasons for these trends are discussed by country, along with sources of uncertainty (particularly large for Siberia). Catches were allocated to Large Marine Ecosystems to present ecosystem-relevant baselines for the impact of fisheries on the Arctic, which can be expected to increase, as industrial fisheries move into a warming Arctic following the invasion of boreal species, unless countries apply precautionary ecosystem-based management approaches.