Pelagic Fish Larvae Research Articles

Investigating the impact of cross-shelf transport and local retention in the Black Sea Rim Current system on small pelagic fishes

Advection of pelagic fish larvae through ocean currents is a source of dispersal that is known to structure marine populations by directly impacting population success and persistence. To be able to understand fish population dynamics and manage existing fisheries it is therefore of importance to assess the extent of exchange between populations and determine the factors that drive it, which is still a challenge in fisheries research today. In this study, the output of a high-resolution basin-scale circulation model is used to calculate the dispersal probability from spawning areas and the remaining Black Sea for a range of commercially important fish such as anchovy, sprat, turbot, red mullet, and bluefish under different environmental conditions. The common trait of many commercially important species in the Black Sea is that they have pelagic larval stages of different time scales which are simulated by tracking virtual drifters in the simulated surface circulation of the Black Sea. Simulation results show that the dynamic current structure of the Black Sea causes low local retention of larvae. During spring and summer lower offshore transport and higher local retention is observed than in fall and winter, which is directly related to the Rim Current strength. The lowest offshore transport is observed on the northern northwestern shelf, the main spawning area for pelagic fish with still 24-32% of larvae transported offshore. Simulations show that pelagic fish species such as anchovy and sprat adopted different reproductive strategies through their species-specific traits. For the summer spawning species anchovy, timing, and location of spawning together with its short pelagic larval stage is shown to enhance retention on the northwestern shelf. Sprat with its long pelagic larval stage and winter spawning is more adapted to high offshore transport, making it unlikely that sprat is recruited to the same area as where it is spawned. This modeling framework provides a basis for investigating recruitment variability of pelagic fish species in the Black Sea specifically considering the impact of climate variability and provides a useful guide to the potential connectivity of marine populations or the spread of invasive pests in the Black Sea.

Growth–feeding linkage in small pelagic fish larvae in the Kii Channel, Japan

AbstractThe linkage between growth rate and feeding success has been shown to strengthen the effects of early growth rate on later growth rate in the early life history of fish. However, the growth–feeding linkage largely remains to be tested at the individual level within the same populations/cohorts. We examined the growth–feeding linkage for multiple populations/cohorts in Japanese anchovy Engraulis japonicus larvae and Pacific round herring Etrumeus micropus larvae, through otolith microstructure analysis, based on samples collected from the commercial fishery for larval fish in the Kii Channel, Japan. The three growth–feeding mechanisms, which are based on the respective potential advantages of larger somatic size, higher growth rate, and earlier morphological development for achieving feeding success, were tested to understand how growth rate relates to feeding success. The “somatic size” mechanism was supported for all of six samples for anchovy larvae and three of four samples for round herring larvae. The “growth rate” mechanism was supported for two of six samples for anchovy larvae and three of four samples for round herring larvae. The “morphological development” mechanism was supported for three of four samples for anchovy larvae and all of three samples for round herring larvae. Overall, the present analysis supported the growth–feeding linkage but revealed the dynamics of the growth–feeding mechanisms. All the mechanisms were shown to operate at least for certain populations/cohorts, but none of them were universally effective over all populations/cohorts across the two species. Understanding the dynamics of the growth–feeding mechanisms would provide precious hints for considering strategies of predicting recruitment dynamics.

Fish bioacoustics: Navigating underwater sound.

Fish bioacoustics is about the sounds produced by fish, how fish hear, and what they hear. The focus of this article is on the hypothesis that some late pelagic stage reef fish larvae use the marine soundscape to locate reef settlement habitat. The hypothesis is evaluated by consideration of the nature of reef sound, hearing ability in late-stage larval fish, and direct behavioral evidence for orientation to reef sound.

First feed matters: The first diet of larval fish programmes growth, survival, and metabolism of larval ballan wrasse (Labrus bergylta)

The use of cleaner fish, such as the ballan wrasse (Labrus bergylta), is important for combatting the sea lice problem in salmonid cage farming. Ballan wrasse is the only wrasse species that is cultivated, though only about 50% of the approx. 3 million ballan wrasse used in 2020 was produced by aquaculture. The major obstacle for large scale cultivation of ballan wrasse is the difficult first feeding phase and a lack of functional feeding protocols.Like most pelagic marine fish larvae, ballan wrasse do not accept inert diets as first feed, and feeding regimes based on rotifers and Artemia (brine shrimps) usually lead to mixed results and are far from being optimal nutrition for the larvae.In a 48-day start feeding experiment, we studied the feasibility of replacing rotifers by an Experimental cirriped diet or copepod nauplii (Acartia tonsa) and replacing Artemia by nauplii of the cirriped Semibalanus balanoides. Later, all treatments received the same formulated diets. We sampled larvae at each feed transition to analyze different response variables such as growth, morphometry, gene expression, lipidomics, histology, and microbiology.We found significant differences in survival rates and growth. Larvae fed copepods as the first diet had significantly higher survival rates than larvae start-fed on either rotifers or small experimental cirripeds, and this pattern was also reflected in early growth and bone development. Gut histology at the end of the experiment (48 days after hatching) showed a more developed intestinal tissue in the larval group fed copepods first and cirripeds as the second diet compared to the other larval groups.Gene expression at day 48 post hatch still revealed pronounced differences between the larval group first fed on rotifers and larvae from the other three feeding regimes which received natural, unenriched diets. Even weeks after receiving the same formulated diets, lipidomics analyses revealed that several lipid species correlated either negatively or positively with larval growth rates or mortality.Our results are a clear indication for nutritional programming, pointing towards the importance the first diet has for the further life of a fish.

Diel Vertical Distribution Patterns of Pelagic Fish Larvae in Yilan Bay, Taiwan

To study the diel migration distribution of larval fish in an area adjacent to the Kuroshio Current, samples were collected from six depths by using a Motoda horizontal net at a fixed station in Yilan Bay on July 30 and 31, 2007. A total of 591 larval fish were collected and assigned to at least 34 families and 57 species. The first five dominant species were Benthosama pterotum (40.95%), Diaphus B type (12.18%), Callionymidae spp. (8.46%), Gobiidae spp. (6.60%), and Apogonidae spp. (4.0%). The density of larval fish varied across time. The maximum larval density was 1220.34 individuals/1000 m3 at 19:00, and the minimum larval density was 81.84 ind./1000 m3 at 14:00. The vertical distribution of species accounting for more than 10% of all fish caught was determined by the diurnal and nocturnal migration of the dominant species B. pterotum, which migrated from a depth of 50 m at night to 200 m in the afternoon. The distribution models for other species (e.g., Diaphus B type) were also analyzed in this study.

Export of pelagic fish larvae from a large Great Lakes connecting channel

Export of pelagic fish larvae from a large Great Lakes connecting channel

The relationship between Oceanographic Parameters and Fish Larvae Dispersal in the Fisheries Management Area of the Republic Indonesia (FMA) 717

Cendrawasih Bay and the Pacific Ocean are known as potential fishing areas and as fish spawning locations in Fisheries Management Area 717. Larval dispersal in the waters is strongly influenced by oceanographic parameters. This study was conducted to examine the relationship between oceanographic parameters and fish larval dispersal in FMA 717. This research was conducted using KR Bawal Putih III in November 2019. A number of 42 stations were determined for observation. Environmental parameters included temperature, salinity, dissolved oxygen, chlorophyll-a, turbidity, and photosynthetic active radiation (PAR), were measured using SBE 19 plus V2 CTD while pelagic fish larvae were collected using a bonggo net. Analysis of the correlation of oceanographic parameters with pelagic fish larvae abundance and spatial distribution was calculated using PCA (Principal Component Analysis) statistical analysis. The results showed that the pelagic fish larvae was influenced by temperature, salinity, PAR, chlorophyll-a, turbidity, and DO. Temperature and salinity have a direct interaction to the abundance of pelagic fish larvae.

Latitudinal transition of mesopelagic larval fish assemblages in the eastern central Atlantic

This study presents a broad-scale view of larval fish species distributions in the eastern Central and North Atlantic and places it in a hydrographic context. Pelagic fish larvae, including metamorphic stages, were sampled to 1000 m depth across a 46° latitudinal transect from the equator to the Bay of Biscay. By analysing species composition and relating it to hydrographic parameters, we were able to identify 5 assemblages: Equatorial, Tropical, Subtropical, Temperate-bloom and Temperate-nobloom. We also categorized 4 groups of species by association with specific hydrographic parameters. Tropical species, including Vinciguerria nimbaria, Ceratoscopelus warmingii, and Hygophum macrochir, are associated with high sea surface temperature. Tropical-subtropical species, such as Diogenichthys atlanticus, Benthosema suborbitale and Electrona risso, are associated with high temperature in the upper 200 m, i.e. the epipelagic zone. The Temperate species group, dominated by Benthosema glaciale and Maurolicus muelleri, is associated with high chlorophyll-a in the epipelagic zone, and these species were abundant where the spring bloom occurred. Species with the broadest latitudinal distributions, such as Cyclothone braueri and Argyropelecus hemigymnus, here termed Cosmopolitan species, are associated with high salinity in the epipelagic zone. The Cape Verde Frontal Zone seems to act as a one-way distributional barrier, confining many Tropical larval species to the South Atlantic Central Water mass, while allowing more northerly-distributed species to cross southward. This may be related to a dependence of Tropical species on high near-surface water temperatures, which decrease sharply at the Cape Verde Frontal Zone. An oxygen minimum zone had no significant effect on larval abundance or species richness, although there were some taxonomic differences. For example, phosichthyids, including Vinciguerria nimbaria, were not found within the oxygen minimum zone, while the family Melamphaidae thrived. Our results suggest that the dominant hydrographic factors that affect the distribution of fish larvae in the eastern Central and North Atlantic vary by latitude and by species. The Cape Verde Frontal Zone and oxygen minimum zone play complex roles, affecting different taxonomic groups in various ways.

Does consistent individual variability in pelagic fish larval behaviour affect recruitment in nursery habitats?

Individual animals across all taxa differ consistently in behaviour, i.e. they show personality traits. This inter-individual variability has significant ecological and evolutionary consequences, since it affects a range of population-level processes. Here, we focus on the selection and recruitment of nursery habitats in temperate fish larvae. The “Sense Acuity and Behavioural Hypothesis” has proposed that fish larvae could detect and follow environmental cues to actively choose suitable nursery habitats. We empirically tested this hypothesis questioning if this non-random active process occurs and if it could be linked to consistency in individual behaviours. Individual larvae of the white seabream Diplodus sargus (Linnaeus, 1758) were tested repeatedly at different ages in a two-channel choice-chamber apparatus exposing them to a flow with different stimuli, as nursery habitats (lagoon, coastal), different temperatures or salinities and recording exploratory activity and preference in the different conditions. Most larvae changed behaviour during ontogeny, but they were also significantly consistent in their behaviour, revealing strong individuality; yet, no significant preference for the presented stimuli emerged, nor it was related to individuality. Exploratory activity was higher when larvae showed unresponsive or inconclusive behaviours, meaning that the larvae tried to find a different stimulus from the one that we were offering or had random habitat selection. Individual behavioural consistency could influence the process of searching for suitable nursery habitats and, consequently, dispersion and connectivity of white seabream population. Characterizing the behaviour of temperate pelagic marine fish larvae may shed light on fish recruitment variability, help refining larval dispersion models and possibly help understanding effects of climate change on population distribution and connectivity. A Chinese idiom says that “It is easier to change mountains and rivers than to alter one’s character.” What about fish? Well, fish can exhibit individuality traits that control autoecological and demecological processes. For example, shy fish have lower fitness while the rate of invasion progress is faster in populations with bolder individuals. Individuality studies rarely focused on fish larvae, except for coral fish. So, we tested if temperate fish larvae display consistent behaviour throughout ontogeny. This goal delves into the Sense Acuity And Behavioural Hypothesis which incorporated behaviour into the hypotheses deeming to explain fish recruitment variability. We found that temperate fish larvae display consistent individual behavioural differences in exploratory activity since early in ontogeny. This confirms the deterministic role of pelagic fish larvae behaviour on population connectivity processes, namely to control their dispersion and choose a nursery habitat.

Ichthyoplankton community structure on the shelf break off northeastern Brazil.

Oceanographic features influence the early stages of fish to a high degree. We investigated the influence of continental shelf-slope gradient on the ichthyoplankton composition and distribution off Northeastern Brazil. Two oceanographic campaigns were performed during July-August 2010 and 2012. The samplings were performed along three transects composed by three stations, covering the continental shelf and slope areas. Abiotic data were obtained by an ADCP and a CTD. The ichthyoplankton was sampled through diurnal and nocturnal hauls using a 500-µm bongo net from 200 m to the surface. A total of 1634 larvae and 4023 eggs, representing 91 genera and 76 species, were collected. Higher concentrations of fish eggs were found on the continental shelf, probably because of the North Brazil Undercurrent flux. Higher concentrations of larvae were found at night and could be associated with net avoidance or natural variation. Neritic, oceanic and transition groups of species association were determined. Larvae of neritic, demersal and pelagic fishes prevailed on the continental shelf, while larvae of oceanic, mesopelagic and bathypelagic fishes on the continental slope. Melanostomiidae, Scorpaena sp., Lestidium atlanticum, Lampadena sp. and Diaphus sp. were identified as indicators of the continental slope.

Swimming Abilities of Temperate Pelagic Fish Larvae Prove that They May Control Their Dispersion in Coastal Areas

The Sense Acuity and Behavioral (SAAB) Hypothesis proposes that the swimming capabilities and sensorial acuity of temperate fish larvae allows them to find and swim towards coastal nursery areas, which are crucial for their recruitment. To gather further evidence to support this theory, it is necessary to understand how horizontal swimming capability varies along fish larvae ontogeny. Therefore, we studied the swimming capability of white seabream Diplodus sargus (Linnaeus, 1758) larvae along ontogeny, and their relationship with physiological condition. Thus, critical swimming speed (Ucrit) and the distance swam (km) during endurance tests were determined for fish larvae from 15 to 55 days post-hatching (DPH), and their physiological condition (RNA, DNA and protein contents) was assessed. The critical swimming speed of white seabream larvae increased along ontogeny from 1.1 cm s−1 (15 DPH) to 23 cm s−1 (50 and 55 DPH), and the distance swam by larvae in the endurance experiments increased from 0.01 km (15 DPH) to 86.5 km (45 DPH). This finding supports one of the premises of the SAAB hypothesis, which proposes that fish larvae can influence their transport and distribution in coastal areas due to their swimming capabilities. The relationship between larvae’s physiological condition and swimming capabilities were not evident in this study. Overall, this study provides critical information for understanding the link between population dynamics and connectivity with the management and conservation of fish stocks.

Spatial and temporal variation in the distribution and abundance of pelagic fish eggs and larvae off Giresun, south-eastern Black Sea, Turkey

Background. Giresun Bay is an important spawning ground of many migratory fish species and hence it has been a major fishing area of pelagic fishes in the Turkish territorial waters of the Black Sea. However, this area has not been evaluated thoroughly for the abundance and distribution of pelagic fish eggs and larvae, which are prerequisite for understanding the dynamics of fluctuating fish populations. The presently-reported study aimed to fill this gap in the existing knowledge of spatial and temporal variation in the distribution and abundance of ichthyoplankton in the south-eastern Black Sea. Materials and methods. Bimonthly surveys were carried out from January through November 2009 at inshore and offshore sites (>38°E, >40°N). The samples were collected by horizontal tows with Manta nets. The mouth of the net was equipped with flowmeters to measure the amount of water passing through the net during each tow. Results. The horizontal tows returned a total of 13 556 eggs and 1304 larvae representing 26 species (from 22 families): Engraulis encrasicolus, Sprattus sprattus, Merlangius merlangus, Gaidropsarus mediterraneus, Atherina boyeri, Scorpaena porcus, Chelidonichthys lucerna, Dicentrarchus labrax, Trachurus mediterraneus, Diplodus annularis, Sciaena umbra, Mullus barbatus, Gymnammodytes cicerelus, Ctenolabrus rupestris, Symphodus ocellatus, Trachinus draco, Uranoscopus scaber, Parablennius sanguinolentus, Parablennius tentacularis, Blennius sp., Ophidion rochei, Callionymus pusillus, Gobius sp., Arnoglossus kessleri, Buglossidium luteum, Pegusa lascaris. Overall, the dominant species were E. encrasicolus with 89.8% of all collected eggs, followed by G. mediterraneus (7.0%). Similarly, 47.4% of the total larvae were represented by E. encrasicolus, followed by P. sanguinolentus (22.8%) and S. sprattus (13.2%). The colder months (January, March, and November) presented a total of four species: S. sprattus, B. luteum, Gymnammodytes cicerelus, and Gaidropsarus mediterraneus. The warmer months had a greater variety of different species than colder months. Of these, E. encrasicolus was the most dominant species, providing the maximum abundance of fish eggs and larvae in September. The abundance of E. encrasicolus eggs and larvae decreased from offshore toward inshore sites highlighting the preference of this species to deeper waters for spawning as well as for nursery purposes in Giresun Bay. Conclusion. The results of this study suggest that the length of the closed fishing season in the Black Sea should be reconsidered. We suggest that it should be extended to include also the last week of September in order to provide more time for pelagic fish (e.g., E. encrasicolus) to complete their spawning period. This could result in a healthier and more sustainable stock of E. encrasicolus in the Black Sea.

Dose rate estimation of freshwater wildlife inhabiting irrigation ponds in the exclusion zone of the Fukushima Dai-ichi Nuclear Power Plant accident

To assess the risks of ionising radiation to freshwater environments in the exclusion zone of the Fukushima Dai-ichi Nuclear Power Plant accident, the absorbed dose rates to aquatic organisms possibly inhabiting the irrigation ponds were estimated using the ERICA Assessment Tool from 134Cs and 137Cs radioactivity monitoring data for the period 2013 to 2017. In each year, the total dose rates to benthic organisms were in the same or higher levels compared with those to pelagic organisms. Among pelagic organisms, the total dose rates to amphibians, birds, and pelagic fish were two orders of magnitude higher than those to plankton. The total dose rates to insect larvae, which attained a maximum of 130 μGy h−1, were higher than those to the other benthic organisms. The dose rates to benthic organisms increased from 2013 to 2015 and remained constant thereafter. In 50–93% of ponds, the dose rates to at least one taxon of freshwater organism, all of which were benthic organisms, exceeded the ERICA screening level (10 μGy h−1). Comparison of the estimated dose rates with the ICRP's derived consideration reference levels (DCRLs) suggests that radioactive contamination was not likely to damage amphibians, birds, pelagic fish, benthic fish, crustaceans, and insect larvae inhabiting most of the irrigation ponds in the exclusion zone. However, this comparison also suggests that there was some chance of deleterious effects occurring to birds and benthic fish in a limited number of the most severely contaminated irrigation ponds.

Planktonic stages of small pelagic fishes (Sardinella aurita and Engraulis encrasicolus) in the central Mediterranean Sea: The key role of physical forcings and implications for fisheries management

Multidisciplinary studies are recently aiming to define diagnostic tools for fishery sustainability by coupling ichthyoplanktonic datasets, physical and bio-geochemical oceanographic measurements, and ocean modelling. The main goal of these efforts is to understand those processes that control the dispersion and fate of fish larvae and eggs, and thus tuning the inter-annual variability of the biomass of small pelagic fish species. In this paper we analyse the distribution of eggs and larvae as well as the biological features of the two species of pelagic fish, Engraulis encrasicolus and Sardinella aurita in the north-eastern sector of the Sicily Channel (Mediterranean Sea) from ichthyoplanktonic data collected during the 2010 and 2011 summer cruises. We use Lagrangian simulations and satellite data (i.e., sea surface temperature, wind, and chlorophyll-a concentration) to recognize the main oceanographic patterns that mark eggs and larvae transport processes. We provide a mechanistic explanation of a cross-shore transport process by using a potential vorticity (PV) model that takes into account the role of wind stress in generating cold filaments. Our results show that the strong offshore transport towards Malta occurred in 2010 was likely due to a persistent Mistral wind forcing that generated high-PV cold filaments. This phenomenon was not found in the 2011 analysis, which indeed showed an along-shore transport towards the retention area of Capo Passero. Since, for the first time, we describe the spatial distribution of the early life stage of Sardinella aurita in the northern part of the Sicily Channel and we clarify the link between the ocean dynamics and the fate of small pelagic fish larvae, this work provides a useful, diagnostic tool for the sustainable management of fishery resources.

Anticipating the free amino acid concentrations in newly hatched pelagic fish larvae based on recently fertilized eggs and temperature

Anticipating the free amino acid concentrations in newly hatched pelagic fish larvae based on recently fertilized eggs and temperature

Two deep-living rhodaliids (Cnidaria, Siphonophora) from the Mid-Atlantic Ridge

ABSTRACTRhodaliids are a semi-benthic family of 14 physonect siphonophore species found in all oceans, except the Mediterranean and Arctic. They inhabit species-specific depth ranges in isolated locations and records are mostly sparse. Here, the first ever observations of rhodaliids from the Mid-Atlantic Ridge are given, from three images of two putative species. They come from depths of 3482 and 3667–3670 metres, on the Mid-Atlantic Ridge (MAR) at 23°N and 26°N, near two hydrothermal vents. Rhodaliids are very delicate animals and extremely hard to sample, particularly from such great depths, and the only comparable deep-living species so far described is the Galapagos Dandelion (Thermopalia taraxaca) from 2480–2938 metres on the Galapagos Rift and East Pacific Rise. This species inhabits the outer zone of certain hydrothermal vents where there is no hydrogen sulphide in the water, but connectivity with the MAR species is unlikely, since the latter inhabit a different ocean basin. Two, or possibly three, rhodaliid species have so far been collected in the North Atlantic, and all occurred near continental margins. These new observations are therefore important, and the images included here will hopefully alert future expeditions to hunt for, and perhaps even collect, more specimens. Rhodaliids are mostly observed individually adhering to a variety of substrata with their long tentacles, but very occasionally abundances of from 1 to 11 individuals m−2 have been noted. Rhodaliids feed on copepods, other small pelagic crustaceans and fish larvae, and can thus represent important members of deep-sea ecosystems. This paper provides a distribution map of all species with an accompanying table showing coordinates, depths and number of specimens collected, and a second table of comparative diagnostic rhodaliid characters, which is used to suggest possible identities for the two putative new MAR species.

Diversity of planktonic fish larvae along a latitudinal gradient in the Eastern Atlantic Ocean estimated through DNA barcodes.

Mid-trophic pelagic fish are essential components of marine ecosystems because they represent the link between plankton and higher predators. Moreover, they are the basis of the most important fisheries resources; for example, in African waters. In this study, we have sampled pelagic fish larvae in the Eastern Atlantic Ocean along a latitudinal gradient between 37°N and 2°S. We have employed Bongo nets for plankton sampling and sorted visually fish and fish larvae. Using the cytochrome oxidase I gene (COI) as a DNA barcode, we have identified 44 OTUs down to species level that correspond to 14 families, with Myctophidae being the most abundant. A few species were cosmopolitan and others latitude-specific, as was expected. The latitudinal pattern of diversity did not exhibit a temperate-tropical cline; instead, it was likely correlated with environmental conditions with a decline in low-oxygen zones. Importantly, gaps and inconsistencies in reference DNA databases impeded accurate identification to the species level of 49% of the individuals. Fish sampled from tropical latitudes and some orders, such as Perciformes, Myctophiformes and Stomiiformes, were largely unidentified due to incomplete references. Some larvae were identified based on morphology and COI analysis for comparing time and costs employed from each methodology. These results suggest the need of reinforcing DNA barcoding reference datasets of Atlantic bathypelagic tropical fish that, as main prey of top predators, are crucial for ecosystem-based management of fisheries resources.

Validation of an Eulerian population model for the marine copepod Calanus finmarchicus in the Norwegian Sea

Calanus finmarchicus is an important zooplankton species in the Norwegian Sea, as a dominant food organism for pelagic fish larvae, and a potentially large source of marine lipids and proteins. Its position in the marine food web also makes it an important model species in assessing the risk posed by oil spills in the Norwegian and Arctic Seas. In this study, an Eulerian population model for C.finmarchicus, coupled to the physical and ecological model SINMOD, is presented. The model includes the full life cycle of C. finmarchicus with a representation of all developmental stages. The model has been validated against field measurements made in different areas of the Norwegian Sea in 1997 and 1998. The model displays geographical and temporal distributions of development stages that is in line with observed patterns. When comparing time series for selected regions, we see a high degree of variability both in the field samples and model output. On average, the model deviations are near half of the summed variability of the field data and model estimates.The model has applications within assessment of ecological production, and the potential for harvesting in the Norwegian and Arctic Seas, but in combination with other models, also for the assessment of ecological effects of oil spills and other types of pollution.

Systems approach modelling of the interactive effects of fisheries, jellyfish and tourism in the Catalan coast

Despite the large fluctuation in annual recordings of gelatinous plankton along the Catalan coast in the north western Mediterranean and the lack of long term data sets, there is a general perception that jellyfish abundances are increasing. Local authorities are concerned about the stranding events and arrivals of jellyfish to beaches and believe it could reduce the recreational appeal of the beaches – a valuable ecosystem service for the regional tourist industry. Previous studies also demonstrate the predation of jellyfish (Pelagia noctiluca ephyrae) upon some small pelagic fish larvae (Engraulis encrasicolus). Small pelagics are the principal source of revenue for the local fisheries. A social-ecological model was created in order to capture the effects of changes in abundance of P. noctiluca upon the local fisheries, the tourist industry and the wider economy. The following sub-models were constructed and connected following the systems approach framework methodology: an age-class based fisheries model; a jellyfish population matrix model; a jellyfish stranding model; a study on the impact of jellyfish strandings on beach users; and an economic input–output matrix. Various future scenarios for different abundances of jellyfish blooms were run. The “Expected blooms” scenario is similar to the quantity and size of blooms for 2000–2010. For a hypothetical “No blooms” scenario (standard background level of jellyfish but without any blooms) landings would increase by around 294 tonnes (5.1%) per year (averaged over 10 years) or approximately 0.19 M€ in profits per year (4.5%), and strandings would decrease by 49%. In a “Frequent blooms” scenario, landings would decrease by around 147 tonnes per year (2.5%) and decrease profits by 0.10 M€ per year (2.3%), and strandings would increase by 32%. Given the changes that these scenarios would cause on the regional gross domestic product and employment, this study concludes that the overall impact of either of these scenarios on the economy would not be significant at the regional scale.

Late winter larval fish assemblage in the southern East China Sea, with emphasis on spatial relations between mesopelagic and commercial pelagic fish larvae

We examined larval fish assemblages in the southern East China Sea during late winter where large spawning grounds of several commercial pelagic fishes are formed. Our samples include a total of 187 species or taxa of larval fish belonging to 118 genera, 96 families, and 18 orders. Mesopelagic fish larvae, mainly Stomiiformes, Aulopiformes, and Myctophiformes, accounted for 66.5% of the total catch, while commercial species such as Trachurus japonicus, Scomber spp., and Trichiurus japonicus for 16.6%. Based on the species composition, three assemblages were recognized: Kuroshio (KUR), Shelf-Break (BRE), and Shelf (SHE) assemblages. KUR assemblage was mainly characterized by various mesopelagic fishes such as Sigmops gracilis, Diaphus spp., and Myctophum asperum, BRE assemblage by both commercial pelagic and mesopelagic species, SHE assemblage by demersal species such as Lepidotrigla spp. and Gobiidae spp. Both abundance and diversity were highest in KUR assemblage, although food availability for the larvae would be poorest. The combination of variables of sea surface temperature-chlorophyll a concentrations best explained the larval distribution. Except for Benthosema pterotum, the center of distribution of mesopelagic fish larvae was clearly separated from that of the commercial species by the Kuroshio front. However, a northward intrusion of the Kuroshio transported mesopelagic fish larvae onto the shelf, forming the BRE assemblage. Competition for prey between mesopelagic and commercial pelagic fish larvae would potentially occur if the intrusion is strong.