Pelagic Fish Research Articles

Anchovy boom and bust linked to trophic shifts in larval diet

Although massive biomass fluctuations of coastal-pelagic fishes are an iconic example of the impacts of climate variability on marine ecosystems, the mechanisms governing these dynamics are often elusive. We construct a 45-year record of nitrogen stable isotopes measured in larvae of Northern Anchovy (Engraulis mordax) in the California Current Ecosystem to assess patterns in food chain length. Larval trophic efficiency associated with a shortened food chain increased larval survival and produced boom periods of high adult biomass. In contrast, when larval food chain length increased, and energy transfer efficiency decreased, the population crashed. We propose the Trophic Efficiency in Early Life (TEEL) hypothesis, which states that larval fishes must consume prey that confer sufficient energy for survival, to help explain natural boom-bust dynamics of coastal pelagic fishes. Our findings illustrate a potential for trophic indicators to generally inform larval survival and adult population dynamics of coastal-pelagic fishes.

Differences in the Synergic Accumulation of Toxic Elements in Pelagic and Benthic Fish from Glacier-Fed Rivers of the Dzungarian Alatau

Abstract The determination of potentially toxic element concentrations in fish is an important topic from the point of view of both nature conservation and human consumption. The aim of this study was to assess the concentrations of S, K, Ca, Cr, Mn, Fe, Zn, Rb, Sr, Mo, and P in benthic and pelagic fish species in the Karatal river, which is fed by melting glaciers from the Dzungarian Alatau in Kazakhstan. In September 2022, 48 fish samples were collected. It has been demonstrated that the accumulation of chemical elements in fish species can be explained by both the physiological parameters of the fish species and the influence of glaciers that feed river habitats. The data presented in this study provide a synergistic view of pollutants affecting fish populations. Benthic fish contained more manganese and strontium than pelagic species, while the mutual accumulation of potassium, chromium, rubidium, and molybdenum was higher in pelagic fish. The synergistic concentration of calcium and phosphorus in pelagic fish was higher than that in benthic species, while the amount of zinc and sulfur was higher in benthic animals. Relatively elevated levels of mercury in fish were found. The study contributes to the discussion about the role of glacial environments in loading pollutants to aquatic systems.

Microplastic contamination in edible marine fishes from the upper Gulf of Thailand

Seafood consumption is a major source of microplastic exposure for humans. Here, we demonstrated microplastic contamination in marine food fishes from the upper Gulf of Thailand. Microplastics were found in gastrointestinal tracts of 46.9 % of fishes sampled, with a mean concentration of 1.6 ± 0.5 pieces per fish or 0.04 ± 0.01 pieces/g of fish tissue. Demersal fishes had higher contamination rates than pelagic fishes. Fibrous-type and blue-colored materials were the most abundant microplastics, while the most common polymers were polyester and polyethylene. No associations between microplastics and histopathological changes were detected. Estimated daily microplastic exposure for human marine fish consumers was 0.03 to 0.1 pieces per person. Although we expect a low risk of microplastic contamination in fish muscle because of very low calculated transfer rates, we recommend continuing surveillance, including evaluations of contamination in the food chain to ensure future seafood safety in this region.

Model of mesopelagic fish predation on eggs and larvae shows benefits of tuna spawning under full moon

AbstractMost mesopelagic fish are small planktivores that migrate up at nightfall to feed in the safety of darkness and descend to depth at dawn to escape visual predators. However, the trophic roles can reverse since mesopelagic fishes also predate eggs and larvae of their predators. We use the Atlantic bluefin tuna as a model species to test the hypothesis that fishes in the open ocean synchronize spawning to moon‐lit nights (when mesopelagic fishes avoid near‐surface waters) to increase offspring fitness. Our analysis over two decades of field observations shows that tuna spawn most intensively the week before full moon. This fits predictions from a mechanistic model where spawning around full moon increases offspring fitness by two orders of magnitude due to low predation from mesopelagic fishes. Circalunar patterns of food availability can also favor fitness of offspring spawned the days before full moon. Our findings suggest that mesopelagic fishes may have an important impact on pelagic fish through predation of early life stages and cause an evolutionary drive to synchronize spawning to the lunar cycle.

Fishery potencies as environmental services of Pongok Islands, Bangka Belitung Province

One of the islands with huge potential for fishery in South Bangka Regency is the Pongok Islands. Most of the people living in the islands depend on marine and fishery resources. This research aimed to figure out fishery potencies located in the surrounding island of Pongok related to capture fishery, fish food processing, and aquaculture. Data were gathered on field observation and interviews conducting on August 2022. Results of the research three main fishery activities in this area are capture fishery, fish product processing, and aquaculture. The capture fishery is taken for pelagic and coral fish. Some economic fish are anchovy, sardine, squids, and mackerel kingfish. Harvesting each commodity is different due to species and season of wind blowing as well as fishing gear. Fish products of the island are marketed in Toboali, Pangkal Pinang, and Belitung, and even transported to Pontianak and Jakarta. Aquaculture activity is only conducted for raising groupers using floating nets. Moreover, environmental aspects of mariculture, two new fishery commodities like seaweeds and pearl oysters, have the potential to be introduced into the islands. Environmental services have still contributed directly and indirectly to the fishery activities on the islands now and then.

Parasitic load of the Pacific mackerel, Scomber japonicus (Pisces: Scombridae) from Northwestern Baja California, Mexico.

Globally, the exploitation of small pelagic fish, like Pacific mackerel is of great importance due to food industry demand. However, there are few studies regarding its parasites load and there are no in this geographic zone. This study aimed to assess the parasitic composition, some temporal changes (during spring and summer) in abundance, prevalence and intensity of infection parasitic of the Pacific mackerel (Scomber japonicus) from Todos Santos Bay, Baja California, Mexico. The parasite fauna of the Pacific mackerel consisted of 1930 parasites (1413 in spring and 517 in summer) distributed in the follow taxa: an Tetraphyllidea (Cestoda), Kuhnia scombri (Monogenea), Didymozoidae (Digenea), Anisakis sp. (Nematoda), Rhadinorhynchus sp. (Acanthocephala) and Caligus pelamydis (Copepoda). The nematodes parasite were the most abundant both in spring with a mean abundance of 27.6 parasites and in summer 8.2 parasites compared with the other taxa like Cestoda, Monogenea, Digenea, Acanthocephala and Copepoda (P = 0.003). The mean intensity of the nematodes in spring and summer was 28.1 and 13.4, respectively. The nematodes prevalence was 90 % in spring and 60 % in summer. In general, the parasite load is more abundant in spring than summer. In summer, absence of taxa as Cestoda and Copepoda were registered. Nematode larvae were present in the fish guts mesentery and inside of the stomach, pyloric caeca, intestine. Also the nematodes were found in the liver, muscle and gonads. The most affected organ by nematodes was the intestine mesentery. The most predominant parasite of this study has been Anisakis sp. during spring.

Toxicity risks associated with heavy metals to fish species in the Transboundary River – Linked Ramsar Conservation Site of Tanguar Haor, Bangladesh

The presence of trace metals in aquatic ecosystems can have detrimental effects on fish survival. The Tanguar haor, a Ramsar conservation wetland, receives sediment and water from multiple transboundary rivers. However, there have been limited studies on the metal concentrations in fish species in this sediment-rich wetland. This study aimed to analyze the concentrations of iron (Fe), manganese (Mn), chromium (Cr), copper (Cu), zinc (Zn), cadmium (Cd), and lead (Pb) in water, sediment, and fish tissues. Higher concentrations of Cd and Pb were found in the water and sediment. All these metals were detected in eight fish species, including benthic and pelagic species. Among them, Systomus sarana, a pelagic fish that also consumes benthic organisms, exhibited a higher metal pollution index than other fish, particularly benthic species. The release of higher metal concentrations from sediment into the water has the potential to impact the accumulation of metals in fish. SynopsisThis study on metal concentrations in fish species will aid policymaking on ecotoxicology research for transboundary river-connected wetlands.

Karakteristik Ikan Pelagis Kecil Yang Dipasarkan Di Pasar Arumbai, Kota Ambon

Small pelagic fish play a crucial role in the marine food chain and have significant economic value, yet information about them remains scarce. This research aims to map the origin and characteristics of small pelagic fish marketed at Arumbai Market in Ambon City. The study was conducted over six months, from May to October 2023, at Arumbai Market. The research utilized survey methods and interviews, and the data were analyzed descriptively. Observations were made on the quantity and size structure of four dominant fish species from five different fish landing locations: Hila, Tulehu, Laha, Hitu, and Latuhalat. The results of this research revealed variations in the composition of dominant small pelagic fish species sold, from the highest to the lowest, namely Decapterus sp, Rastreligger sp, Selar sp, and Auxis sp. The contribution of the five fish landing locations is as follows: Hila (31%), Hitu (24%), Tulehu (18%), Laha (15%), and Latuhalat (12%). Differences in the composition of the quantity and size marketed are suspected to be due to variations in seasons, fishing tools, and capture areas.

Influence of migrant Western Regional shark fishers on shark fishing practices along the eastern coastline of Ghana

Sharks have formed an integral part of Ghana’s fisheries for many years, although in many areas outside the Western Region, they are often captured as bycatch. The shark fishery in the Dangme communities along the eastern coastline of Ghana has, however, over the last decade, acquired a commercial character that is believed to have been influenced by migrant fishers from the Western Region. This study thus sought to characterise the influence of the migrant fishers in the development of the thriving shark fishery in Dangme communities. Data collection was through key informant interviews, questionnaire administration to 180 randomly selected native and migrant fishers from the selected communities, and observations of fishing practices. Until the mid-2000 s, only the migrant fishers carried out targeted shark fishing along the Dangme coastline. Presently, however, a significant number of native fishers have redirected their fishing efforts towards shark fishing in the face of dwindling catches from the small pelagic fisheries, which were the primary target of the fisheries. Accounts 75 % of native fishers indicated that the declines in small pelagic fish stocks coupled with the influence of the migrant shark fishers have acted synergistically to influence the shark fisheries dynamics along the Dangme coastline. Despite the average ages of the native and migrant fishers being fairly the same (∼36 years), the migrants possessed a more profound understanding of the marine ecosystem where they operated based on historical antecedents and their longer interactions with the shark fishing zones. Presently, this new fishery, like shark fishing in other shark fishing hotspots in Ghana, is unregulated, but it will be imperative for national fisheries authorities to implement some management measures to reduce fishing pressure on the most vulnerable species.

Summer Biomass Variability and Spatial Interactions between European Sprat (Sprattus sprattus) and Moon Jellyfish (Aurelia aurita) in the Western Part of the Black Sea

Over the past few decades, various causal connections between commercial small pelagic fish species and gelatinous zooplankton have been reported in the Black Sea, which affect the pelagic ecosystem. Recently, moon jellyfish regained dominance among gelatinous plankton; however, biomass fluctuations and interactions with small pelagic fish remain poorly understood. During the summers of 2019–2022, scientific pelagic trawl surveys in the Western Black Sea enabled simultaneous monitoring of small pelagic fish biomass, with sprat as the key species and moon jellyfish as an incidental catch. In total, 153 trawl hauls were conducted across four depth strata from 15 to 100 m, and a “swept area” method was used for biomass estimation. The sprat stock biomass ranged from 10,698 to 29,177 t, with an average value of 19,432 ± 4834 t. The total biomass of moon jellyfish was 2002 ± 868.73 t, and dense aggregations were observed in the coastal waters during certain years. Two scenarios of spatial interactions between planktivorous species were identified and linked to the formation of A. aurita aggregations. We found that changes in jellyfish density were associated with weak-to-moderate effects on the spatial distribution of sprat assemblages in coastal areas.

Suitable habitat of the scad fish (Decanters spp.) in Northern South China Sea predicted by MaxEnt model

As a pivotal economic pelagic fish species inhabiting in upper-middle layers, the scad fish (Decapterus spp.) was assumed a vital role in relieving the fishing pressure imposed upon demersal fish in Northern South China Sea (nSCS). To enhance production and sustain the prominence of the scad fish, this study combined species occurrence data of spanning the spring (March to May) and the autumn (September to November) seasons from 2018 to 2020, and contemporaneous environmental data for prognosticating habitat distribution patterns by the maximum entropy model (MaxEnt). The environmental factors considered were sea surface temperature (SST), sea surface salinity (SSS), sea surface height (SSH), and chlorophyll-a concentration (Chla). The findings highlighted that the application of MaxEnt for each month yielding exemplary results typified by AUC values exceeding 0.9. During the spring, the suitable habitats for the scad fish were observed from the east waters of Hainan to the eastern Guangdong waters, where the centers of gravity was within. Similarly, the suitable habitats in the autumn were delineated within the bounds of the eastern Hainan Island waters to and few waters in eastern Guangdong. The key factors influencing occurrence probabilities of the scad fish varied seasonally, SST and SSS were most important in the spring, SSH and Chla manifested the greatest contribution to in the autumn. By elucidating spatiotemporal habitat suitability, this study may furnish robust scientific foundations to optimize catches and identify primary fishing grounds for the ecologically and economically vital species, facilitating sustainable resource utilization.

Hasil Tangkapan Mini Pure Seine Di Perairan Teluk Ambon Luar Dan Selatan Pulau Ambon

A purse seine is an active fishing gear used by fishermen in Ambon Island to catch small pelagic fish that gather in high abundance, although the information is still limited. The purpose of this research is to determine the species composition and size distribution of the catch from the mini purse seine in the waters of Outer Ambon Bay (TAL) and South Ambon Island (SPA). From the results of this research, there are four types in TAL waters and two types in SPA. In TAL, the captured fish species were Decapterus sp (Scad), Selar sp (Selar), Sardinella sp (Sardine), and Rastreliger sp (Mackerel). Sardine had the highest catch percentage at 28.41%, followed by scad (25.28%), mackerel (23.27%), and selar (23.04%). In the SPA waters, only scad (Decapterus sp) and selar (Selar sp) were found, with catch percentages of 57.83% and 42.17%, respectively. The average size distribution of scad caught with the mini purse seine in TAL waters was 16.62 cm, selar (17.22 cm), sardine (13.36 cm), and mackerel (17.34 cm). In SPA waters, the average size distribution of scad was 17.59 cm, and selar (16.63 cm).

Author Correction: No state change in pelagic fish production and biodiversity during the Eocene–Oligocene transition

Author Correction: No state change in pelagic fish production and biodiversity during the Eocene–Oligocene transition

Biological information on a rare pelagic fish, black ruff Centrolophus niger, caught in Icelandic waters: Distribution, feeding, and otoliths.

Black ruff (Centrolophus niger) is a rare and poorly studied species found in both the Atlantic and Pacific Oceans and also in the Mediterranean Sea. It is sporadically caught south of Iceland during the annual International Ecosystem Summer Survey of the Nordic Seas. In total, 43 specimens were caught from 2009 to 2021, of which 41 specimens were caught during 2017-2021. All specimens, except one, were caught using a pelagic trawl (cod-end mesh-size: 50 mm) close to the surface (trawl depth: 0-35 m) with in situ temperature ranging from 9 to 13°C. The area south of Iceland is characterized by having warmer temperatures than other areas around the island, which might be indicative of a northern limit for the distribution of black ruff. The fish were primarily in the range of 29-46 cm with a few larger individuals up to 71 cm. Fourteen fish, caught in 2017 and 2021, were dissected to gather biological information on this species. These fish were all juveniles with no obvious sign of gonad development. Correlations between total length, fork length, and standard length are presented. Otoliths were thin and delicate with a length of ~13-16 mm, and otolith size (length, width, and area) was correlated with fish size. Much of the stomach content was at an advanced stage of digestion, but some contents could be identified and consisted of invertebrates, primarily of the orders Amphipoda and Calanoida with some unidentified fish also present.

Reproductive biology of the mackerel scad, Decapterus macarellus (Cuvier, 1833), in the Sulawesi Sea, Indonesia

Indonesia is the second largest fishery producer in the world, producing many small pelagic fish. To improve information for sustainable fishery management in the Sulawesi Sea, we examined the reproductive biology of the main target species, the mackerel scad Decapterus macarellus (Cuvier, 1833). Between May 2020 and March 2021, we collected 1267 mackerel scads from two landing sites in northern Sulawesi. These fish ranged from 13.4 to 38.2 cm in total length, and their sex ratio, length at first maturity (Lm), reproductive periodicity, and potential spawning grounds were studied. An equal male to female (M:F) sex ratio of 0.98:1.00 was osberved. The lengths of males and females at first maturity (Lm) were 22.59 and 21.62 cm, respectively. The mackerel scads spawned throughout the year, peaking in January, March, May, and September. Spawning occurs mainly during the first quarter of the moon’s phase. Most mature individuals with a high gonadosomatic index were found near Tumumpa Dua and the northern and western coasts of the Sangihe and Siau Islands, suggesting that there are specific locations where mackerel scads spawn. Fishery managers can use this information to implement temporary and regional fishing closures to develop sustainable fishing practices for small pelagic fish species.

Evaluating robustness of harvest control rules to climate-driven variability in Pacific sardine recruitment

Climate-driven changes in ocean temperatures, currents, or plankton dynamics may disrupt pelagic forage fish recruitment. Being responsive to such impacts enables fisheries management to ensure continued sustainable harvest of forage species. We conducted a management strategy evaluation to assess the robustness of current and alternative Pacific sardine harvest control rules under a variety of recruitment scenarios representing potential projections of future climate conditions in the California Current. The current environmentally informed control rule modifies the harvest rate for the northern sardine subpopulation based on average sea surface temperatures measured during California Cooperative Oceanic Fisheries Investigations field cruises. This rule prioritizes catch at intermediate biomass levels but may increase variability in catch and closure frequency compared to alternative control rules, especially if recruitment is unrelated to ocean temperatures. Fishing at maximum sustainable yield and using dynamically estimated reference points reduced the frequency of biomass falling below 150 000 mt by up to 17%, while using survey index-based biomass estimates resulted in a 14% higher risk of delayed fishery closure during stock declines than when using assessment-based estimates.

Some biological aspects of indian mackerel (Rastelliger kanagurta Cuvier, 1817) in Bali Strait waters

Indian mackerel (Rastrelliger kanagurta Cuvier, 1817) is a small pelagic fish species which is the main catch commodity in purse seine and jukung fleets in the Bali Strait waters. Sustainable management is urgently needed for indian mackerel populations in Bali Strait waters to remain sustainable fishery. The availability of basic information such as biological aspects is very important as a fundamental resource in the management of indian mackerel in Bali Strait waters. The aims of this study were to reveal several biological aspects of mackerel such as growth patterns, condition factors, sex ratio, and size at first maturity of indian mackerel in Bali Strait waters. Sampling was carried out in May-September 2018. Samples of fish were taken from purse seine and jukung fleets using trawl nets and gill nets. Fish sample was measured, weighed and dissected to observe the sex and the gonadal maturity stage. The total number of indian mackerel samples was 167 individuals. Mackerel in the Bali Strait waters has a positive allometric growth pattern with fish in good condition. The sex ratio was in an unbalanced condition with the number of male fish being more than the female fish. The size at first maturity was 19.34 cm for male fish and 19.76 cm for female fish.

Ectopleura crocea (Cnidaria: Hydrozoa) Identified as a Predator of Pelagic Fish Eggs through Cytochrome c Oxidase I Metabarcoding

Fish eggs have a wide range of predators. However, observing these predators is challenging, as is identifying fish eggs based on morphological traits. In this study, we observed hydroids, which are sessile organisms, consuming pelagic fish eggs. We conducted cytochrome c oxidase I (COI) metabarcoding to identify both the predator and the prey species. Massive COI reads were de novo assembled and nine representative sequences were constructed. The predator, identified from the representative sequences and its morphological features, was determined as Ectopleura crocea. The fish eggs that had been preyed upon belonged to two species: Sillago japonica and Parajulis poecilepterus. Additionally, four arthropod species (Labidocera rotunda, Oithona similis, Paracalanus parvus, and Pseudevadne tergestina) were consumed, and their morphological traits could not be observed, due to digestion. COI metabarcoding was an effective tool for studying the feeding activity of these small predators.

Evaluation of alternative harvest policies for striped bass and their prey, Atlantic menhaden

Ecosystem approaches to fisheries management are being explored worldwide, but few evaluations of multispecies harvest control rules (HCRs) exist. Our goal was to perform a simulation test of a suite of HCRs using an age-structured predator–prey model to represent the dynamics of a small pelagic fish, Atlantic menhaden ( Brevoortia tyrannus), and its predator, striped bass ( Morone saxatilis). We evaluated a suite of static and dynamic single and multispecies HCRs to estimate effects on stock performance metrics. No single HCR achieved ecosystem management objectives for both stocks given their current reference points, but HCRs that involved the “40–10 rule” for striped bass performed well across all predator performance metrics. The most influential factor determining performance of striped bass HCRs was striped bass fishing mortality, and relatively few HCRs achieved target SSB for Atlantic menhaden. Our study indicated that some HCRs recommended for forage fish management may not be effective in systems with generalist predators, and that ecosystem management objectives might be achievable by simultaneously adopting HCRs for both predator and prey stocks that complement one another.

Isotopic signatures induced by upwelling reveal regional fish stocks in Lake Tanganyika

Lake Tanganyika’s pelagic fish sustain the second largest inland fishery in Africa and are under pressure from heavy fishing and global warming related increases in stratification. The strength of water column stratification varies regionally, with a more stratified north and an upwelling-driven, biologically more productive south. Only little is known about whether such regional hydrodynamic regimes induce ecological or genetic differences among populations of highly mobile, pelagic fish inhabiting these different areas. Here, we examine whether the regional contrasts leave distinct isotopic imprints in the pelagic fish of Lake Tanganyika, which may reveal differences in diet or lipid content. We conducted two lake-wide campaigns during different seasons and collected physical, nutrient, chlorophyll, phytoplankton and zooplankton data. Additionally, we analyzed the pelagic fish–the clupeids Stolothrissa tanganicae, Limnothrissa miodon and four Lates species–for their isotopic and elemental carbon (C) and nitrogen (N) compositions. The δ13C values were significantly higher in the productive south after the upwelling/mixing period across all trophic levels, implying that the fish have regional foraging grounds, and thus record these latitudinal isotope gradients. By combining our isotope data with previous genetic results showing little geographic structure, we demonstrate that the fish reside in a region for a season or longer. Between specimens from the north and south we found no strong evidence for varying trophic levels or lipid contents, based on their bulk δ15N and C:N ratios. We suggest that the development of regional trophic or physiological differences may be inhibited by the lake-wide gene flow on the long term. Overall, our findings show that the pelagic fish species, despite not showing evidence for genetic structure at the basin scale, form regional stocks at the seasonal timescales. This implies that sustainable management strategies may consider adopting regional fishing quotas.