Abundance Of Fish Larvae Research Articles

Coastal winds and larval fish abundance indicate a recruitment mechanism for southeast Australian estuarine fisheries

AbstractCoastal winds transport water masses and larval fish onshore or offshore which may influence estuarine recruitment, yet our understanding of the mechanism underlying this relationship is limited. Here, we combine datasets from a historical database of larval fish off southeast Australia with a high‐resolution atmospheric reanalysis model to show that normalised abundance of coastally spawned larvae increased with weak to moderate upwelling favourable winds 14 days prior to sampling. The increase in abundance may reflect increased nutrient and plankton availability for larval fish. Normalised larval abundance decreased following strong upwelling favourable winds but increased after onshore (downwelling favourable) winds, due to wind‐driven transport. By combining a commercial estuarine fisheries catch‐rate dataset (4 species, 8 estuaries, 10 years) and the high‐resolution atmospheric reanalysis model, we show that negative effects of upwelling favourable winds during the spawning period can be detected in lagged estuarine commercial fisheries catch rates (lagged by 2–8 years depending on species' growth rates), potentially representing the same mechanism proposed for larval fish. Upwelling favourable winds in the southeast Australian region have increased since 1850 while onshore winds have decreased, which may have reduced larval recruitment to estuaries. Coastal winds are likely an important factor for estuarine recruitment in the southeast Australian region and future research on the estuarine recruitment of fish should incorporate coastal winds.

Going with the flow: Spatio‐temporal drift patterns of larval fish in a large alpine river

Abstract Fish larval drift is an essential step in the life cycle of riverine fish species as it determines dispersal and colonisation. Anthropogenic flow alterations and interruption of longitudinal and lateral connectivity by river damming and straightening can severely affect larval drift patterns. In this study, we characterised spatio‐temporal drift patterns of fish larvae in the heavily regulated large alpine River Inn and within a constructed nature‐like fish bypass. Drift was investigated in the main reproduction period of the fish fauna in this river, ranging from mid‐April to end of June. Diel patterns were assessed by samples taken during day, dusk, night, and dawn each day of sampling. To obtain robust species identification, we used DNA barcoding for genetic verification of phenotypically pre‐sorted groups. From a total of 1,069 fish larvae and 283 fish eggs caught, DNA barcoding revealed 16 species from five families, including several target species of conservation. We found strong evidence that several endangered species, such as Chondrostoma nasus, Thymallus thymallus, Cottus gobio, and Aspius aspius successfully reproduced in the bypass system. Genetic species verification showed a high level of homogeneity in most phenotypically pre‐sorted groups. Distinct seasonal patterns were observed, with the majority of fish species in the drift observed in mid‐June. Thymallus thymallus and Cottus gobio dominated larval drift at the beginning of the observation followed by mainly unimodal abundance peaks of several Cyprinid species. Nocturnal drift prevailed in all species. Our results on the spatial occurrence and abundances of fish larvae highlight the importance of bypass systems in heavily modified waterbodies to provide valuable spawning habitats and drift corridors around dams. Moreover, the distinct species‐specific time patterns of larval drift represent a first basis to direct future discharge and river management plans in large alpine rivers towards a protection of the sensitive larval stages of specific target species of conservation. This includes bypass and turbine operation modes in the period of highest drift activity, as well as the construction of nature‐like bypass systems and creation of spawning grounds therein.

Effect of coastal development on larval fish abundance in Klang Strait (Malaysia)

Changes in larval fish assemblages were studied before (1985–86) and after (2013–2014) rapid coastal development in the Klang Strait, Malaysia, based on a Before-After-Control-Impact (BACI) experimental design. Fish larvae were sampled by bongo-nets along an 18-km transect from the impact station at the Kapar power station (KPS) to four control stations in increasingly offshore waters. Families Gobiidae, Clupeidae, Sciaenidae and Engraulidae were most abundant at both sampling periods, demonstrating their adaptability and resilience to the natural and anthropogenic disturbances. Coastal development has reduced larval fish abundance at KPS, inevitably shifting higher larval abundance to the control stations. This shift is related to lower sea surface temperature and higher pH. Despite the coastal disturbances, there was an overall increase in total larval fish abundance attributed to the preflexion stage of the Gobiidae, Sciaenidae, Engraulidae, Cynoglossidae and Callionymidae, and the yolk-sac and preflexion larvae of unidentified taxa.

Larval Fish Assemblage Structure at Coastal Fronts and the Influence of Environmental Variability

Within the coastal zone, oceanographic features, such as fronts, can have major effects on the abundance and distribution of larval fish. We investigated the effects of fronts on larval fish assemblages by jointly collecting physical (ADCP and CTD) and biological (larvae) data in the nearshore waters of the south coast of South Africa, on four separate neap-tide occasions. Accumulation of fish larvae at predominantly internal wave-associated fronts was observed, with higher larval densities inshore of and within the front than farther offshore. On each occasion, larvae of coastal species with pelagic eggs (Mugillidae and Sparidae) were numerically dominant at the front itself, while inshore of the front, larvae of coastal species with benthic eggs (Gobiesocidae and Gobiidae) were more abundant. Offshore catches mainly comprised Engraulidae (pelagic species with pelagic eggs) larvae, which were generally restricted to the bottom, where current velocities were onshore on each occasion. On the occasion when fast (>100 cm/s) currents prevailed, however, accumulation of the larvae of coastal species occurred offshore of the front, and larvae were mixed throughout the water column. Thus, larval occurrence at these coastal frontal systems was strongly affected by the degree of mixing by currents, which on most occasions resulted in onshore retention. The results underline the importance of frontal systems in determining the nearshore distributions of fish larvae, particularly by retaining coastal fish species in the inshore region. The environmental variability observed at these frontal systems has potential implications for larval connectivity of fish populations.

Modelling the distribution of larval fish in a western boundary current using a multi-voyage database

Across the world’s oceans, western boundary currents are strengthening and warming faster than the global average. This is expected to have large impacts on the distribution of pelagic fishes, as their dispersal and physiological range limits shift. Monitoring the distribution of larval fish assemblages, sampled with plankton nets, allows for population and community-level responses to climate-driven changes to be observed without reliance on fisheries data. Here, we characterise patterns in the distribution of larval fish over 15° of latitude with highly variable conditions driven by a western boundary current, the East Australian Current, using a newly available larval fish database supplemented with recently collected samples. Using generalized additive mixed models, we show strong non-linear relationships between larval fish taxonomic richness and abundance with latitude. During autumn, winter and spring, both larval fish abundance and richness are greater in equatorward latitudes (28°S) than in more poleward ones (43°S), with this pattern reversed during the summer. The region where the East Australian Current separates from the coast delineates a zone of marked change in larval fish richness and abundance. Analyses of larval fish assemblages using Gaussian copula graphics models revealed a strong association between assemblage composition and temperature. The direction of temperature effects on individual taxa varied greatly, highlighting the complex nature of possible climate-driven shifts. Our study highlights the utility of compiling multi-voyage databases and their role in monitoring the global oceans.

Early Life Stages of Fishes in Lake Taal, Philippines: Assessment and Implications for Biodiversity Management and Conservation

Lake Taal is the third largest lake in the Philippines and its fisheries provide livelihood to thousands of locals in its coastal areas. This study was conducted to recommend possible strategies and measures to conserve and protect the population of fishes, especially of the early life stages (ELS). The composition, abundance, and distribution of ELS and the environmental factors affecting these were investigated through monthly ichthyoplankton surveys and monitoring of water parameters, phytoplankton, and zooplankton abundances in 12 equidistant stations from January 2015 to December 2018. A total of 26,345 fish eggs and 9,140 fish larvae were collected, of which 88.9% of the fish larvae were morphologically identified into eight families, while the rest were unidentified. Families Terapontidae (44.5%) and Gobiidae (37.0%) numerically dominated the identified larvae catch. Distribution of the egg, yolk sac, and pre-flexion stages (ELS) significantly varied across stations. Three stations on the northern basin of the lake showed the highest fish egg abundance (731.82, 246.47, and 381.28 ind 100 m–3) while stations on the west, northwest, and eastern bay of the lake showed the highest abundance of fish larvae (153.76, 121.28, and 94.64 ind 100 m–3). The temporal distribution of ELS was highly associated with zooplankton, green algae, and salinity while spatial distribution was highly associated with the majority of the water parameters and chlorophyll a. Seasonal and annual distribution of ELS showed significant variation, which reveals possible spawning patterns of the identified fish larvae and the influence of varying environmental conditions to the distribution of ELS. Based on these, the identified possible spawning and larval foraging grounds are recommended as protected zones. Reduction of nutrient inputs to minimize changes in the lake trophic condition is also recommended.

Quantitative assessment of fish larvae community composition in spawning areas using metabarcoding of bulk samples.

Accurate assessment of larval community composition in spawning areas is essential for fisheries management and conservation but is often hampered by the cryptic nature of many larvae, which renders them difficult to identify morphologically. Metabarcoding is a rapid and cost-effective method to monitor early life stages for management and environmental impact assessment purposes but its quantitative capability is under discussion. We compared metabarcoding with traditional morphological identification to evaluate taxonomic precision and reliability of abundance estimates, using 332 fish larvae from multinet hauls (0-50m depth) collected at 14 offshore sampling sites in the Irish and Celtic seas. To improve quantification accuracy (relative abundance estimates), the amount of tissue for each specimen was standardized and mitochondrial primers (12S gene) with conserved binding sites were used. Relative family abundance estimated from metabarcoding reads and morphological assessment were positively correlated, as well as taxon richness (RS =0.81, P=0.007) and diversity (RS =0.90, P=0.002). Spatial patterns of community composition did not differ significantly between metabarcoding and morphological assessments. Our results show that DNA metabarcoding of bulk tissue samples can be used to monitor changes in fish larvae abundance and community composition. This represents a feasible, efficient, and faster alternative to morphological methods that can be applied to terrestrial and aquatic habitats.

An assessment of the larval fish diversity within a coastal marine reserve: Larval fish diversity within a marine reserve

Knowledge of ichthyoplankton diversity and distribution is important in the management of a fishery for increased productivity and to ensure sustainability. In the Discovery Bay Special Fishery Conservation Area (DBSFCA) and other marine protected areas in Jamaica, there is a paucity of information on larval fish communities and the factors affecting their diversity and distribution. Therefore, we compared the efficiencies of light traps and plankton nets to assess the richness and composition of ichthyoplankton species in Jamaica’s oldest fish sanctuary, the DBSFCA. Min/Max Auto-correlation Factor Analysis (MAFA) and the Dynamic Factor Analysis (DFA) were then used to compare biotic and abiotic factors that influenced larval fish diversity and distribution. A total of 41 species belonging to 39 families of predominantly reef-associated species were identified during the sampling period of February to November 2014. The plankton net proved to be more efficient, catching 2202 individuals from 36 species, while light traps caught 590 individuals from 15 larval fish species. The plankton nets and light traps collected 27 and seven mutually exclusive species, respectively. From February to July, Clupeidae and Pomacentridae dominated the larvae community and throughout the study period Clupeidae was the most abundant family in the light traps. Blennidae, Gobiidae, Labridae, Labrisomidae, Pomacentridae and Sparidae frequently accounted for less than 50% of the relative abundance. Commercially important families such as Lutjanidae and Haemulidae were rarely caught with both gears. Additionally, temporal changes in the abundance and richness of fish larvae, indicating peak abundance during July and August, were detected with both DFA and MAFA. A DFA model with two common trends and three explanatory variables (mean day-length, mean zooplankton richness and mean monthly sea temperature) was the optimal model for characterizing ichthyoplankton abundance. The study highlights the importance of incorporating ichthyoplankton surveys in marine reserves especially with the threat of climate change and overfishing.

Diversity, distribution, and abundance patterns of ichthyoplankton assemblages in some inlets of the northern Persian Gulf

Distribution patterns of fish at early life stages can have profound effects on their development and survival. Here, diversity, distribution, and abundance patterns of ichthyoplankton assemblages were investigated in some inlets of the northern Persian Gulf during 2013–2014. A total of 21,440 fish larvae belonging to 30 families were identified, with Clupeidae, Gobiidae and Sillaginidae being the most dominant families. Spatial segregation of stations and species-environmental ordination patterns were observed according to multivariate analyses. Two larger inlets and one which had freshwater input supported higher abundances of fish larvae, whereas the smallest inlet and the sea station were dominated by fish eggs. The highest and the lowest abundances of ichthyoplankton were observed in April and December, respectively. Our results suggest that there are temporal and spatial variations in ichthyoplankton assemblages of the northern Persian Gulf. Both generalized linear mixed model and distance-based redundancy analysis revealed that water temperature, transparency, and depth were the key variables affecting the larval fish abundance. The results of this study provide valuable insights into fish larval ecology in shallow subtropical estuaries and inlets and help to explore how fish larvae respond to space–time environmental conditions.

Variación espacio-temporal de larvas de peces en el golfo de Guayaquil, Ecuador

Este estudio presenta la densidad, composición taxonómica, distribución espacial y temporal de larvas de peces en el golfo de Guayaquil, así como la relación con algunas variables físico-químicas. Se recolectaron muestras en 16 estaciones, tomadas en la primera milla náutica del estuario externo e interior del golfo, ubicadas frente a la provincia de Guayas y noroeste de la isla Puná, durante junio a diciembre de 2012. Se realizaron arrastres superficiales con una red cónica simple (ojo de malla: 300 μm; diámetro de boca: 0,3 m; largo: 1,2 m). La temperatura, salinidad y transparencia fueron medidas antes de cada arrastre. Se detectaron diferencias significativas entre zonas, registrando mayor temperatura, menor salinidad y transparencia en el estuario interior. Se colectaron 321 638 ind/100m3 de larvas de peces, pertenecientes a 13 familias y 36 especies entre la zona externa e interna. Engraulidae (58,9 %) fue la familia más abundante en las estaciones del estuario exterior, seguida de Sciaenidae (22,8 %) y Haemulidae (9,6 %). Las familias más frecuentes en el estuario interior fueron Engraulidae (74,4 %) y Gobiidae (16,1 %). El 85 % de la densidad total fue aportada por cinco especies, de las cuales Anchoa sp. y Bairdiella sp. fueron las más abundantes y dominantes, principalmente durante diciembre. La estructura y composición de la comunidad larvaria fue significativamente diferentes entre áreas (MW-U= 450; p < 0,05) y meses de muestreo (KW=14,24; p < 0,05), con mayores registros en el estuario exterior durante diciembre. Con el análisis de redundancia (ADR) se observa que, en el área externa, las especies estuvieron asociadas con la transparencia del agua, mientras que las especies que concurrieron en la zona interna se relacionaron positivamente con la salinidad. En términos generales, la abundancia y riqueza de larvas de peces en el área externa del golfo de Guayaquil está relacionada con las condiciones de transparencia y salinidad local, las cuales favorecieron a la presencia larval.

Environmental factors affecting the nursery function for fish in the main estuaries of the Gulf of Cadiz (south-west Iberian Peninsula)

Hydrological, geomorphological, physicochemical and biological factors influence the nursery function of estuaries. Our study compared the environmental conditions and the assemblages of early life stages of fish in the main four estuaries of the Gulf of Cadiz (Cadiz Bay, Guadalquivir, Odiel-Tinto and Guadiana). Samples were taken within each estuary and on their adjacent coast, during the dry-warm seasons of 2016, 2017 and 2018. Results showed that rivers with smaller basins had a very low freshwater input and their estuaries, Odiel-Tinto and Cadiz Bay, were essentially sea extensions into the land, containing similar physicochemical conditions to nearshore zones, as well as similar assemblages and densities of early life stages of fish. Open water masses of these estuaries do not have important nursery functions. In contrast, inner zones of estuaries with bigger basins and higher freshwater discharges, Guadalquivir and Guadiana, have different environmental characteristics and a long transition zone with a well-defined salinity gradient. Their assemblages and densities of early life stages of fish were different between them and with other estuaries. The Guadalquivir estuary held the highest abundance of larval and early juvenile fish, as well as macrozooplankton biomass. The most abundant fish species in all zones of every estuary was the anchovy Engraulis encrasicolus; the Guadalquivir inner zone had the highest density. High concentration of suspended organic matter, provided by freshwater input and correlated with total suspended solid, suspended inorganic matter and turbidity, was the physicochemical characteristic more typical of the Guadalquivir. This characteristic, in addition to the salinity gradient, could explain the highest densities of macrozooplankton found in this estuary, and consequently, of early fish stages. Recurrent jellyfish blooms were observed in Cadiz Bay and the inner zone of Guadiana, affecting their nursery functions. Odiel-Tinto showed altered physicochemical and biological characteristics, which may need further specific research.

KELIMPAHAN DAN DISTRIBUSI LARVA IKAN DI PERAIRAN PESISIR LAMPUNG TIMUR

Information abundance and distribution of fish larvae in coastal waters of East Lampung currently very limited. The research aimed to improve the knowledge of the early life of organisms, in order to manag biodiversity and biological resources in the waters. Research station representing the several water sectors: in-shore, near-shore, and off-shore. The research was a representation of eastern monsoon (June) and transition monsoon (September) in 2017. Fish larvae was harvested using bon ggo-net tool while its identification to family level using portable Dino-lite . Based on the result the Abundance of fish larvae in eastern monsoon was higher than transition monsoon. This research found 81 families of fish larvae. There were 10 dominant families, that are Gobiidae, Pegasidae, Mullidae, Pomacentridae, Sillaginiidae, Bleniidae, Bythitidae, Carangidae, Pseudochromidae and Bothidae. The distribution of fish larvae in the lower in-shore was higher than near-shore and off-shore, while east and transitional seasons have not much different larval catches. Temperature, salinity and pH parameters indicated optimal range state for survival and growth of fish larvae, brightness and turbidity in accordance with water quality standards, currents velocity on eastern monsoon is very fast while transition monsoon is fast to very fast. Phytoplankton and zooplankton showed sufficient natural food availability for the life of fish larvae. Result Canonnical Corespondence Analysis (CCA) analysis to connectivity of abundance and larvae distribution showed that the brightness parameter forming a point projection while other water environment condition parameters form a vector projection in both period of monsoon. The abundance and fish larvae distribution in coastal waters of East Lampung in all three sectors of the waters had proportionality to the parameters of environmental conditions, especially the current parameters and the difference of the monsoon period.

ИХТИОПЛАНКТОН АВАЧИНСКОЙ ГУБЫ В 2014–2017 ГГ.

Species composition of ichthyoplankton community was analyzed, relative abundance of eggs and fish larvae and seasonal changes in the qualitative composition of ichtyoplankton catches was estimated based on the data of the complex researches in Avachinskaya Bay in 2014–2017. In general 25 species from 11 famelies were found for the whole period of researches in the waters of Avachinskaya Bay. The eggs and the larvae revealed in our catches represented the families, including Pleuronectidae, Gadidae, Cottidae, Ammodytidae, Agonidae, Hexagrammidae, Liparidae, Osmeridae, Ptilichthyidae, Stichaeidae and Scorpaenidae. The ichthyoplankton in Avachinskaya Bay consisted in 92% of eggs and in 8% of larvae. The ichthyoplankton complex was the most reach and abundant in April and May.

COMPOSITION AND DISTRIBUTION OF FISH LARVAE SURROUNDING THE UPWELLING ZONE IN THE WATERS OF NORTHEASTERN TAIWAN IN SUMMER

We investigated the species composition and distribution of fish larvae surrounding the upwelling zone in the waters of northeastern Taiwan in July 2011. The surface water had higher temperatures (25.7°C-28.3°C) and lower salinity (33.67-34.05 psu) than did lower water columns. A divergent trend was observed between temperature and salinity in the waters above 80 m. Moreover, we identified a cold-core eddy at the upwelling of the Kuroshio subsurface at waters approximately 60 m beneath the surface. In total, 1834 fish larvae were collected from eight stations; 85 taxa contributing to 60 families were identified. The abundance of fish larvae varied among stations. The five predominant larval taxa, which constituted 50% of the total fish larvae, were Auxis spp. (30.14%), Sciaenidae spp. (6.73%), Decapterus spp. (6.29%), Champsodon spp. (5.52%), and Gobiidae spp. (4.83%). Higher diversity and lower evenness index values were recorded in areas of high temperature and low salinity. Two larval fish assemblages, Mixed Coastal Group and Upwelling Group, were identified from a cluster analysis. Mixed Coastal Group exhibited higher density, higher temperature, and lower salinity than Upwelling Group did. Thus, in general, the density, spatial distribution, composition, and diversity of fish larvae differed, and the salinity at the 20-m layer exerted a more substantial effect on larval distribution in this study.

Evaluation of the influences of dam release types, land use, and habitat affecting abundance, richness, diversity, and community structure of larval and juvenile fish

We systematically evaluated the influence of dams on downstream aquatic habitat and early life stage (ELS) fish at two spatial scales from epilimnetic and hypolimnetic discharges and made comparisons with a control stream. ELS fish exhibited a general increase in abundance, richness, and Shannon diversity with increasing distance from dams in both epilimnetic and hypolimnetic release types. Nonmetric multidimensional scaling (NMDS) indicated larval and juvenile fish communities were structured differently between epilimnetic and hypolimnetic releases, and habitat variables structuring those communities were more variable in epilimnetic releases than in hypolimnetic releases. Rapid changes occurred within the first 1100 m reach and a second more gradual gradient extended beyond the 5100 m sample reach. Generally, our findings agreed with that of the Serial Discontinuity Concept (SDC), but we believe future studies should be explicit in the systematic evaluation of the SDC, and further studies are required to understand the two recovery gradients that exist below impoundments.

Density‐ and size‐dependent mortality in fish early life stages

AbstractThe importance of survival and growth variations early in life for population dynamics depends on the degrees of compensatory density dependence and size dependence in survival at later life stages. Quantifying density‐ and size‐dependent mortality at different juvenile stages is therefore important to understand and potentially predict the recruitment to the population. We applied a statistical state‐space modelling approach to analyse time series of abundance and mean body size of larval and juvenile fish. The focus was to identify the importance of abundance and body size for growth and survival through successive larval and juvenile age intervals, and to quantify how the dynamics propagate through the early life to influence recruitment. We thus identified both relevant ages and mechanisms (i.e. density dependence and size dependence in survival and growth) linking recruitment variability to early life dynamics. The analysis was conducted on six economically and ecologically important fish populations from cold temperate and sub‐arctic marine ecosystems. Our results underscore the importance of size for survival early in life. The comparative analysis suggests that size‐dependent mortality and density‐dependent growth frequently occur at a transition from pelagic to demersal habitats, which may be linked to competition for suitable habitat. The generality of this hypothesis warrants testing in future research.

Ихтиопланктон и трофические взаимоотношения в планктонных сообществах прибрежной акватории Юго-Западного Крыма (Чёрное море) в летний сезон 2013 г.

В прибрежной акватории Юго-Западного Крыма летом 2013 г. изучены видовой состав и количественные показатели мезо-, макро- и ихтиопланктона, а также питание личинок рыб. В ихтиопланктоне обнаружены икра и личинки 33 видов рыб из 24 семейств, что вдвое превысило показатели 1990-х гг. В мае 2013 г. в прибрежной акватории Севастополя наблюдался результативный нерест хамсы, которому способствовали благоприятная температура воды в море (+21 °C) и хорошие кормовые условия. Наибольшее количество летненерестующих видов зарегистрировано в июне при температуре поверхностной воды +22,7 °C. Численность икры рыб в 2013 г. увеличилась по сравнению с таковой в 2000 г. в 3,4 раза, личинок ― в 2,3 раза, что связано с их большей выживаемостью при улучшившихся условиях питания в результате относительно высокой численности зоопланктона с преобладанием мелкоразмерной фракции и доминированием в ней ювенильных стадий копепод. Другими факторами, улучшившими состояние кормовой базы личинок, были низкая численность гребневика Mnemiopsis leidyi A. Agassiz, 1865 и его слабое воздействие

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.

Mesoscale distribution and assemblage structure of fish larvae in the Kuroshio waters off eastern Taiwan

The mesoscale distribution of fish larvae and its relationships with oceanographic features were examined among six cruises from four seasons in the Kuroshio waters off eastern Taiwan between May 2003 and November 2004. A total of 389 taxa (including two morpho-types) of fish larvae belonging to 106 families and 204 genera were identified from the samples. Families with higher numbers of species were Myctophidae, Scombridae, Stomiidae, Paralepididae, and Gobiidae. Maurolicus japonicus (relative abundance, 7.8%), Vinciguerria nimbaria (7.4%), Sigmops gracilis (6.5%), Cyclothone alba (5.5%), and Diaphus stubby type (5.0%) were the five most abundant taxa. Fish larvae abundance was lower in February and August 2004 than in other cruises, but without spatial variation in distribution. Although the predominant species were similar among cruises, species number and diversity were higher in May 2003 and lower in August 2004. Two larval fish assemblages were distinguished, one containing mainly autumn, winter, and spring and the other mainly spring and summer collections. The taxonomically diverse larval fish assemblage demonstrated that the Kuroshio waters off eastern Taiwan are a major transition zone between tropical and subtropical faunas. These communities are enriched by northward advection of larvae and early juveniles of many tropical species into subtropical waters via the Kuroshio Current. In addition, offshore transport of neritic fish larvae also increased the diversity of the larval fish assemblage in Kuroshio waters. The distribution of fish larvae was related to oceanographic features, with surface salinity, chlorophyll, and food sources being correlated to the abundance of fish larvae.

A review of the ecological effects of European Common Reed (Phragmites australis) on fishes and fish habitat in North America

The invasive European Common Reed (Phragmites australis), first established in North America in the early 1900’s, is now a dominant emergent aquatic plant in many coastal and inland wetlands. A review of the literature was conducted to evaluate the extent of ecological impacts on fishes and their habitat, such as changes in the composition and abundance of native fishes and wetland plants, and alterations to water availability and substrate. The review indicated that a reduction in the abundance of native fishes was common (54.54% of studies), as were impacts to fish habitat (e.g., 54.54% of studies documented a change in wetland plant composition). Many studies were conducted in the eastern and northern United States, which showed that the abundance of juvenile and larval fishes was significantly lower in marshes dominated by P. australis, relative to those dominated by native plant species (Spartina alterniflora); however, changes to wetland plant abundance and composition, water availability, water temperature, nutrient cycling, substrate, reproduction and spawning, genetics of native fishes, and general food web effects were also observed. These results indicate that P. australis poses numerous ecological impacts to the structure and function of wetland habitats, with implications for the ongoing productivity of aquatic ecosystems.