Structure Of Ichthyoplankton Assemblages Research Articles

Assemblage Structure of Ichthyoplankton and Its Relationship with Environmental Factors in Late Summer-Autumn and Winter in the Beibu Gulf, China

Being a biologically diversed hotspot in the global marine ecosystem, the Beibu Gulf is inhabited by a high diversity of fish and serves as a vital fishing ground in China. Due to continuous overfishing, the fishery resource has drastically declined in the Beibu Gulf. However, information about the ichthyoplankton assemblages in this area is still lacking. In this present study, ichthyoplankton diversity, spatial and temporal distribution patterns, and assemblage structures were examined using the specimens collected in the late summer–autumn and winter of 2022 in the Beibu Gulf, and the relationship between ichthyoplankton assemblage and environmental variables was studied. A total of 117 ichthyoplankton taxa, belonging to 13 orders and 42 families, were recorded. The most abundant families were Gerreidae, Leiognathidae, and Sillaginidae in late summer–autumn, accounting for 38.74%, 27.95%, and 9.94%, respectively. Sparidae, Platycephalidae, and Sillaginidae were the most abundant families in winter, accounting for 34.03%, 17.15%, and 8.20%, respectively. Cluster analysis identified five assemblages in late summer-autumn and four assemblages in winter. The most characteristic species in each cluster were Terapon jarbua, Sillago sihama, Leiognathus brevirostris, Mene maculate, and Scomberoides tol in late summer-autumn and Scomberomorus commerson, Acanthopagrus latus, Sillago sp., and Evynnis cardinalis in winter. The results of the canonical correspondence analysis indicated that pH, chlorophyll-a (Chl-a), depth, dissolved oxygen (DO), sea surface salinity (SSS), total nitrogen (TN), and total phosphorus (TP) were the major environmental variables affecting the ichthyoplankton assemblage structure in the Beibu Gulf. The finding of this study will provide valuable information in conserving fish spawning grounds and developing fishery management practices to protect fishery resources in the Beibu Gulf.

Genetic Identification of Ichthyoplankton in the Black Sea and Their Abundance and Community Assemblages

Accurate identification of fish species during the planktonic stages is vital for detecting spawning, foraging, and growth sites of fish species to provide data for stock assessment, environmental impact assessment, and ecological monitoring. In this study, seasonal ichthyoplankton abundance, community composition, and main possible environmental drivers that influence their community composition were investigated in the Southeastern Black Sea. Ichthyoplankton samples were seasonally collected for a year from four stations, two coastal and two offshore sites. DNA barcoding method was applied to identify ichthyoplankton specimens. Of 33 ichthyoplankton taxa identified using DNA barcoding, 31 taxa were identified at species level and 2 taxa were identified at genus level due to unavailability of reference sequences from the Black Sea in public databases. Engraulis encrasicolus, Sprattus sprattus, Mullus barbatus, and Trachurus mediterraneus were identified as the most abundant species. Engraulis encrasicolus alone accounted for nearly 91.5% of the total catch. Seasonality had a strong influence on the ichthyoplankton assemblages. The highest ichthyoplankton abundance was found in summer, followed by winter, autumn, and spring. While 30 fish taxa were identified in summer, 10 taxa were identified in spring, 3 taxa were identified in both autumn and winter. Ichthyoplankton communities were dominated by E. encrasicolus, M. barbatus, and T. mediterraneus specimens in summer, S. sprattus, and M. merlangus specimens in winter, S. sprattus and G. mediterraneus specimens in autumn, Alosa immaculata and Merlangius merlangus in spring. The ichthyoplankton abundance and richness was generally higher in coastal stations in each season. Engraulis encrasicolus, S. sprattus, M. merlangus, P. incognitus were the only species that detected in more than 4 hauls. On the other hand, M. batrachocephalus, P. flesus, S. abester, T. draco, U. cirrosa, and C. lucerna were only detected in a single haul. Overall, the dominant environmental variable affecting abundance of ichthyoplankton was temperature. The relationship between community composition and environmental variable based on nMDS analysis indicated that ichthyoplankton assemblage structure is also influenced by salinity, dissolved oxygen, chlorophyll-a, NO2, and NO3.

Assessment of the Brazilian Coast Oil Spill Impact in the fish eggs and larvae development from the Tropical Continental Shelf

The response of ichthyoplankton assemblage to the oil spill in the coastal region of Brazil Northeaster on August 2019 was investigated using data of before and after spill from plankton survey off the coast of Salvador. Differences in fish egg and larvae density was evident in all samples collected in the continental shelf of Salvador, after oil spill (Oct/2020 and Feb/2021). In general larvae larger than 5 mm tended to occur predominantly before oil spill, while smaller larvae (1–3 mm) occurred predominantly after oil spill, mainly in October/2020. Abnormalities in embryonic development, deformity in the spine and yolk sac edema were found in fish eggs and larvae sampled in the Salvador continental shelf. Rate of abnormalities in embryonic development were significantly increased after oil spill (Oct/2020, Feb/2021) compared to before oil spill period (Oct/2013, Feb/2014) and high incidence of larvae with spinal deformities was observed after oil spill, about 65% of the larvae sampled in the BA 2 station on October 2020 presented deformity in the spine. The fluid accumulation in the yolk sac (edema) were observed only after oil spill on October 2020. The results of this study indicate negative impact of oil spill in the coastal region of Brazil Northeaster on structure of ichthyoplankton assemblages in the continental shelf of Salvador.

Spring Ichthyoplankton Assemblage Structure in the Yangtze Estuary Under Environmental Factors

Estuaries, where fresh and salty water converge, provide abundant nutrients for ichthyoplankton. Ichthyoplankton, including fish eggs, larvae, and juveniles, are important fishery recruitment resources. The Yangtze Estuary and its adjacent waters comprise a typical large-scale estuary and supply many important fish spawning, feeding, and breeding areas. In this study, 1,291 ichthyoplankton individuals were collected in the Yangtze Estuary in spring, from 2013 to 2020. The aims of the study were to provide detailed information on characteristics of the ichthyoplankton assemblage, explore interannual variation, and evaluate the effects of environmental variables on the temporal variation in assemblage structure. Twenty-six species in seventeen families were identified. The dominant species were Coilia mystus, Chelidonichthys spinosus, Engraulis japonicus, Hypoatherina valenciennei, Larimichthys polyactis, Salanx ariakensis, Stolephorus commersonnii, and Trachidermus fasciatus. The ichthyoplankton assemblage changed significantly over time, and Chelidonichthys spinosus became one of the dominant species. Canonical correspondence analysis showed that temperature and chlorophyll a were the key factors affecting the assemblage structure in the Yangtze Estuary in spring.

Assemblage Structure of the Ichthyoplankton and Its Relationship With Environmental Factors in Spring and Autumn off the Pearl River Estuary

Ichthyoplankton assemblages and their relationship with environmental variables are investigated in waters off the Pearl River Estuary in spring and autumn of 2019. Of 80 ichthyoplankton taxa identified using DNA barcode and morphological methods, 61 are identified to species. The most abundance families (Carangidae, Trichiuridae, Mullidae, and Scombridae) account for 61.34% of the horizontal total catch in spring, while Menidae and Carangidae are the most abundant families identified in autumn, accounting for 89.72% of the horizontal total catch. Cluster analysis identifies three species assemblages in spring, and four in autumn based on horizontal trawls. Relationships between assemblage structure and environmental variables (in situ and remote sensed) are determined by canonical correspondence analysis. Ichthyoplankton assemblage structure appears to be strongly influenced by sea level anomalies, salinity, water depth, temperature at 10 m depth, and distance from shore. We demonstrate the efficacy of using DNA barcode to identify ichthyoplankton, and suggest how these data can be used to protect fish spawning grounds in waters off the Pearl River Estuary.

Effect of freshwater discharge from Namgang Dam on ichthyoplankton assemblage structure in Jinju Bay, Korea

The movement of fish eggs and larvae in bay and estuarine systems is affected by freshwater discharge. In this study, the assemblage structures of ichthyoplankton eggs and larvae were assessed for the first time in Jinju Bay, South Korea, to identify the spawning and nursery functions of the bay. Fish eggs and larvae and several environmental parameters were sampled monthly from April 2015 to March 2016 inside and outside of the bay. Within the bay we collected eggs and larvae from 25 and 35 species, respectively, indicating greater diversity than outside the bay, where we collected eggs and larvae of 20 and 28 species, respectively. Fluctuations in water temperature and salinity were larger inside than outside of the bay, and chlorophyll-a concentration was higher within the bay, likely due to discharge from the Namgang Dam, which causes water to flow from the inside to the outside of the bay. This process influences fish larva abundance, such that more larvae are found outside than inside the bay. We also found that 28 fish species use Jinju Bay as a spawning ground. For some species, the timing of egg and larva appearance differed inside and outside of the bay, suggesting that the timing of spawning may differ between the two environments.

Spring and summer ichthyoplankton assemblages in a temperate Patagonian gulf: an overview of temporal and spatial patterns on their structure.

Knowing about the spatio-temporal patterns in the structure of ichthyoplankton assemblages allows inferring about the spawning behaviour of adult fishes, understanding the recruitment dynamics, and predicting the potential effects of mid- and long-term changes. Here, we studied the ichthyoplankton assemblages from the San José Gulf (Northern Patagonia, Argentina) and investigated their changes in space and time. To do that, we took monthly samples during two consecutive years, in spring and summer. A total of 2088 larvae were caught; they comprised 36 taxa, from which 14 were identified to species, two to genus, one to family and one to order. There were large differences in the structure of the assemblages between years, coincidently with marked changes in the surface water temperature. The structure of the ichthyoplankton assemblages also showed significant differences between the spring and summer: Helcogrammoides cunninghami, Dules auriga and larvae belonging to the family Engraulidae contributed most to these differences. The species diversity was higher in the colder year than in the warmer one. We discuss the potential role of environmental and oceanographic features on the interannual variability in the early stages of coastal fishes within a small gulf.

Spatial and temporal variation of late summer ichthyoplankton assemblage structure in the eastern Chukchi Sea: 2010–2015

The survival of the planktonic stages of marine fishes is widely considered to be a bottleneck in recruitment success and is a period when fishes are highly sensitive to changes in their environment. In high latitude areas that are forecasted to experience warming temperatures, it is critical to determine a baseline of ichthyoplankton assemblages to detect how the ecosystem may change in response to shifting conditions. This study used ichthyoplankton data from the eastern Chukchi Sea in the summers of 2010–2015 to assess temporal and spatial variation in assemblage structure. Larval densities were examined in relation to oceanographic conditions at depth and corresponding water masses. Additionally, the standard lengths of polar cod (Boreogadus saida), a key trophic link in Arctic food webs, were assessed for size-at-catch relationships. In 2010 and 2011, years of widespread presence of warm, low salinity bottom water masses such as Alaska Coastal Water, yellowfin sole (Limanda aspera) and longhead dab (Limanda proboscidea) dominated the assemblages. In 2012 and 2013, the increased presence of colder, more saline Winter Water coincided with a shift to polar cod-dominated assemblages. In 2014 and 2015, water masses were less spatially defined and different assemblages, characterized by Arctic sand lance (Ammodytes hexapterus) and saffron cod (Eleginus gracilis), were detected than previous years. The greatest range in sizes of polar cod was observed in 2014, as well as the highest number of juveniles and age-1 individuals were collected. The biophysical patterns identified here support the strong connection between interannual oceanographic conditions and ichthyoplankton assemblages which reflect the importance of continuous, multi-year surveys to document assemblage changes in the Arctic.

Long-term trends in ichthyoplankton assemblage structure, biodiversity, and synchrony in the Gulf of Alaska and their relationships to climate

Understanding and tracking how ecosystems respond to changing environments is an ongoing challenge. Marine ecosystems in the North Pacific support productive fisheries and diverse ecosystem services, and they are subject to large-scale environmental, human, and ecological perturbations. Ichthyoplankton time-series from these ecosystems may provide an important indicator of lower trophic level dynamics and ecosystem functioning. Here we present a spatiotemporal analysis using data from three decades of ichthyoplankton surveys in the Gulf of Alaska to investigate temporal patterns in indicators of species richness, Shannon diversity, and synchrony. Then we use Dynamic Factor Analysis (DFA) to synthesize the ichthyoplankton assemblage with two dominant trends. We relate the biodiversity indices and DFA trends to local and regional climate indices in the North Pacific. We find evidence for increased temperatures driving increased species richness, and changes in synchrony coincident with shifting assemblage composition and the 1988/1989 regime shift. Shannon diversity was largely driven by the dominance of larval walleye pollock (Gadus chalcogrammus). Correlations between climate drivers and DFA trends suggest that the influence of basin scale drivers (North Pacific Gyre Oscillation and the Pacific Decadal Oscillation) were stronger than the influence of local-scale drivers like regional sea surface temperature. Our work demonstrates the potential value of ichthyoplankton surveys to provide indicators of climate-driven ecosystem variability and long-term ecological change.

Ichthyoplankton assemblage structure of springs in the Yangtze Estuary revealed by biological and environmental visions.

The ichthyoplankton assemblage structure in the Yangtze Estuary was analyzed based on four springs in 1999, 2001, 2004 and 2007 in order to provide detailed characterizations of the ichthyoplankton assemblage in springs, examine the long-term dynamics of spring ichthyoplankton assemblages, and evaluate the influence of environmental factors on the spatial distribution and inter-annual variations of ichthyoplankton assemblages associated with the Yangtze Estuary. Forty-two ichthyoplankton species belonging to 23 families were collected. Engraulidae was the most abundant family, including six species and comprising 67.91% of the total catch. Only four species (Coilia mystus, Engraulis japonicus, Trachidermis fasciatus and Allanetta bleekeri) could be considered dominant, accounting for 88.70% of total abundance. The structure of the ichthyoplankton spring assemblage persisted on an annual basis, with the dominant species reappearing consistently even though their abundance fluctuated from year to year. This inter-annual variation probably reflects variable environmental conditions influenced by jellyfish blooms, declining river flow, and overfishing. Canonical correspondence analysis indicated aspatial structure of the ichthyoplankton assemblage in three areas: (1) an inner assemblage dominated by C. mystus; (2) a central assemblage dominated by A. bleekeri and T. fasciatus; and (3) a shelf assemblage featuring E. japonicus. The observed ichthyoplankton assemblage structure appears to be strongly influenced by depth, salinity and suspended particulate matter gradients.

Cross‐Shore, Seasonal, and Depth‐Related Structure of Ichthyoplankton Assemblages in Coastal Alabama

AbstractInvestigations of the spatial and temporal structure of larval fish assemblages are essential for a better understanding of the dynamics of fish populations and their resilience to environmental change. This study provides an original typology of the spatial, seasonal, and depth‐related structure of ichthyoplankton assemblages collected along a 77‐km cross‐shore gradient in Alabama coastal waters. This typology is based on a depth‐discrete ichthyoplankton survey conducted across multiple years at a high spatial and temporal resolution in the northern Gulf of Mexico. A total of 350,766 larvae were collected, among which >95% could be identified to families. The total density of fish larvae was significantly higher inshore, whereas the number of families increased offshore. Multivariate regression trees and Dufrêne–Legendre indices were used to identify seven assemblages dominated by different families of larvae. These assemblages were primarily structured by distance from the shore, followed by season and depth, and were associated with different water masses characterized by distinct temperature and salinity conditions. Families Clupeidae, Bregmacerotidae, Synodontidae, Scombridae, and Ophidiidae were typical offshore, whereas families Engraulidae, Gobiidae, and Gobiesocidae were typical inshore. These observed spatial distributions likely reflected interactions between adult spawning behaviors and oceanographic processes, in particular the influence of the Mobile River. Our results thus confirm existing lines of evidence suggesting that riverine influences play a major role in fish population dynamics along the Alabama inner shelf. For many families, the observed seasonal distributions were largely consistent with the results of previous studies conducted at smaller spatial resolution in the area. However, our large‐scale, high‐resolution, cross‐shore design clearly improved the detection of seasonal variations for inshore and offshore taxa otherwise rarely collected.

Fish larvae assemblage of a coastal area under influence of petrochemical activities, in Todos os Santos Bay, Bahia, Brazil

Todos os Santos Bay, having an area of approximately 927 km2, is the largest Bay on the Brazilian coast. Four sampling surveys, in two rainy and two dry periods, were made at five locations of Todos os Santos Bay, Bahia, Brazil, aiming to identify environmental and ecotoxicological correlates of ichthyoplankton assemblage structure. The study area showed a community characterised by the domination of Engraulididae, Gobiidae (Gobionellus spp.), Gerreidae (Diapterus spp. and Eucinostomus spp.) and Carangidae (Oligoplites spp. and Caranx spp.) larvae. There wasn't a significant difference in composition of fish larvae between the sampling periods, but there was a significant temporal variability in the most important environmental variables. The results showed statistically significant differences between northern stations and the control site, only for ammonium–nitrogen and total fish larvae density. The environmental variables (temperature, ammonium-nitrogen, oil and grease and chlorophyll a) explained 94.7% of the variation of the larval fish assemblage.

Interannual and seasonal variability of the diversity and structure of ichthyoplankton assemblages in the central Mexican Pacific

AbstractWe examined larval fish diversity and assemblage structure off the central coast of the Mexican Pacific from December 1995 through December 1998, including the 1997–98 El Niño event. A total of 132 taxa were recorded, the dominant species being Bregmaceros bathymaster, Dormitator latifrons, and Harengula thrissina (90, 1.9, and 0.8% of the total abundance, respectively). Only B. bathymaster, D. latifrons, and Gobionellus sp. occurred in all samples. The effects of the 1997–98 El Niño on ichthyoplankton diversity were significant, but typical seasonal patterns were also detected. Diversity null models were used to determine the structural changes in the assemblage related to El Niño; both richness and evenness of the species were highest during this event. The most parsimonious models of assemblage organization include El Niño and seasonality as the most significant environmental variability sources. The small‐scale spatial variability expressed as the cross‐shore gradient was not significant. The dominant species group formed by B. bathymaster, D. latifrons, and Vinciguerria lucetia typifies, in terms of similarity, both the pre‐El Niño and El Niño periods; abundance differed between periods. The El Niño period was characterized locally by the dominant Bentosema panamense and H. thrissina, by the rare Euthynnus lineatus, and species of Lutjanus. Seasonality produced changes also in the relative frequencies of the dominant species plus the occurrence of rare forms. The average taxonomical distinctness, considered herein as an indicator of functional diversity, reflected the seasonal variability of the assemblages, aside from El Niño; this index showed lowest values during tropical and transitional periods, both characterized by warm, oligotrophic waters. The high dominance of B. bathymaster in the area and its effect on diversity stabilized the local ichthyoplankton assemblage. An upgraded analysis of diversity allowed a more detailed description of the variability in this assemblage, thus stressing the differential effects of El Niño at distinct latitudes.

Seasonal variation in horizontal and vertical structure of larval fish assemblages off south-western Australia, with implications for larval transport

The coastal ocean off south-western Australia is characterised by the southward-flowing Leeuwin Current, which suppresses the upwelling typically associated with other eastern boundary currents in the southern hemisphere. This results in a unique environment for the transport and survival of planktonic fish larvae. The horizontal and vertical structure of larval fish assemblages off south-western Australia was investigated during winter (August 2003) and summer (January 2004), and related to these unusual regional oceanographic and biological processes. Larval fish were sampled along a four station transect running from the inner continental shelf to offshore waters, using depth-integrated bongo net tows and depth-stratified EZ net tows. The distribution of taxa across the shelf and offshore was strongly influenced by the current regime at the time of sampling. Larval fish assemblage structure reflected the distinctive oceanographic conditions found during each season, and vertical depth distributions of larvae affected their horizontal location. Continental shelf samples were dominated by larvae of pelagic fishes, such as clupeiform species (e.g. Sardinops sagax), whereas offshore assemblages were characterised by larvae of oceanic families, such as Myctophidae and Phosichthyidae. The winter cruise (August 2003) was completed during a time of strong, southerly Leeuwin Current flow, whereas the northward-flowing Capes Current, in combination with surface offshore Ekman transport, predominated during summer. The vertical depth preferences of larvae were particularly influential in affecting their horizontal position; especially so for surface-dwelling larval fishes found during summer. This study represents the first documentation of the vertical structure of ichthyoplankton assemblages in the oligotrophic waters off south-western Australia.

Ichthyoplankton abundance, distribution, and assemblage structure in the Gulf of Alaska during September 2000 and 2001

Autumn ichthyoplankton assemblage structure in the Gulf of Alaska (GOA) region has not previously been characterized. Ichthyoplankton data from September 2000 and 2001 survey collections were analyzed to describe assemblages in the western GOA, to examine interannual variation in assemblages, and to relate observations to oceanographic conditions. Taxa with the highest frequency of occurrence (2000/2001) included Osmeridae (94/87%), Hexagrammos lagocephalus (57/45%), Sebastes spp. (35/47%) and Bathymaster spp. (27/57%). Through the use of clustering techniques and ordination, three identifiable larval assemblages common to both years were identified. Slope assemblages appeared well defined in both years, while nearshore and mid-shelf assemblages tended to be more loosely associated and variable between years. Analyses of environmental variables (temperature, salinity, water depth, distance from shore, and water transport) suggest ichthyoplankton assemblage structure is affected primarily by bathymetry and circulation. We demonstrate that early autumn ichthyoplankton assemblage structure in the GOA is fundamentally linked to variations in macro- (slope vs. shelf) and meso-scale topography (on-shelf proximity to land masses), and suggest that these intrinsic associations may be modified by spatial and temporal variations in local hydrographic conditions.

Cross-shelf and vertical structure of ichthyoplankton assemblages in continental shelf waters of the Southern Gulf of Mexico

The horizontal and vertical variation of ichthyoplankton assemblages in continental shelf waters of the Southern Gulf of Mexico was studied during an annual cycle (1994–1995) at 22 stations distributed across four transects located off the main fluvio-lagoon systems of the area. Samples were collected from five levels of the water column, from the surface to a depth of 105 m. The Bray–Curtis Dissimilarity Index identified five assemblages: Coastal, Inner Neritic, Outer Neritic, Oceanic and a Transition Group. The main species of each assemblage reflected the habitat, season, and spawning area of adult organisms. The Coastal Assemblage occupied the uppermost water column levels of the most nearshore stations. The Oceanic Assemblage was restricted to the deepest samplings of the stations of the outer shelf and the Neritic Assemblages were located on the continental shelf between the Coastal and Oceanic Assemblages, embracing all the sampling levels in some periods. Variation in composition, location and abundance of larvae in each assemblage was determined by a series of physical processes that act at different temporal and spatial scales, especially the mixing process generated by the wind stress and continental water discharges acting at a mesoscale that influences the distribution of the assemblages along the whole continental shelf as well as a fine scale affecting the composition and vertical distribution of organisms in a more reduced area of just tens of meters in the water column. Canonical Correspondence Analysis revealed that the depth of the sample, the potential energy, and the temperature generated the greatest variability in the system. Vertical and horizontal salinity gradients play a determinant role in delimiting the Coastal and Neritic Assemblages.

Ichthyoplankton Assemblage Structure in Mississippi Sound as Revealed by Canonical Correspondence Analysis

The spatiotemporal dynamics of the ichthyoplankton assemblage structure were investigated in Mississippi Sound, a northern Gulf of Mexico estuary. The study was based on a comprehensive survey constituting 528 collections from 22 stations over 12 months at two tow depths. Important environmental correlates of assemblage structure were identified using canonical correspondence analysis (CCA). A wide taxonomic diversity was encountered during the ichthyoplankton survey, including 152 taxa distributed among 48 families. Strong physical gradients in water temperature, dissolved oxygen and salinity correlated predominantly with ichthyoplankton assemblage structure, and reflected substantial spatiotemporal variation. The CCA results were interpreted in light of adult life-style characteristics. Ecological groups of larvae, as defined by adult life-style characteristics for respective taxa, showed distinctive dispersion patterns in 2-dimensional canonical space. A diverse group of offshore demersal taxa clustered as larvae in a region of CCA space corresponding spatiotemporally with stations located in passes and outside of the Sound during late summer and autumn. Other ecological groups, such as the inshore nektonic and offshore pelagic fishes, were widely dispersed as larvae in canonical space, with member taxa occurring under dissimilar physical conditions. Estuarine embayments in the north-central Gulf of Mexico, like Mississippi Sound, might be viewed appropriately as landwardmost sections of the wider, highly productive nursery grounds of this region.