Abundance Of Fish Larvae Research Articles

Spatial-Temporal Abundance and Diversity of Larval Fish in Different Water Bodies (Estuary and Adjacent Coastal Waters) from Sungai Kuala Terengganu, Malaysia

During larval form, various factors will affect the distributions of fish which lead to spatio-temporal variation of their assemblage. Studies on the variation provide knowledge in understanding the fish ecology. Present study aims to survey the fish larval occurrence in the estuary of Sungai Kuala Terengganu and its adjacent waters. A total of 402 larvae samples were collected using a 100 μm mesh sized Bongo net. About 334 samples were identified belonging to 23 families while the rest (equivalent to 16.92% of total catch) were unidentifiable. Three most abundant recorded families are Gobiidae (19.65% of total catch, 2.22 indv. 100 m-3), Ambassidae (12.94% of total catch, 1.47 indv. 100 m-3) and Apogonidae (9.45% of total catch, 1.02 indv. 100 m-3). Based on cluster analysis, fish larvae were divided into two groups whereby one from estuary of Sungai Kuala Terengganu and another one from its adjacent coastal water with little overlapping between them. Estuary observed higher larval density than adjacent coastal waters while larval taxa diversity recorded to be higher in the adjacent coastal waters compared to the estuary. Throughout sampling months, two larval mean density peaks were observed during June 2019 (76.19 indv. 100 m-3) and January 2020 (105.38 indv. 100 m-3).

Abundance and Distribution of Fish Larvae in the Central Coast of the Algerian Sea

Abundance and Distribution of Fish Larvae in the Central Coast of the Algerian Sea

Contrasting distributional patterns of two co-occurring ctenophores in relation to ichthyoplankton and environmental features in the Southwestern Atlantic Ocean

Assessing the ecological role of ctenophores is crucial to understanding ecosystem functioning, including the recruitment of fish stocks. During austral summer in the North Patagonia Ecosystem (NPE) (41-48°S), the ctenophores Mnemiopsis leidyi and Pleurobrachia pileus co-occur with the peak of ichthyoplankton abundance of 2 important fishing resources: the Argentine anchovy Engraulis anchoita and the Argentine hake Merluccius hubbsi, in association with a highly productive tidal front system. We analyzed 367 plankton samples collected in the NPE over 13 yr (2005-2018) to determine the abundance and spatial distribution of M. leidyi and P. pileus, their spatial overlap with ichthyoplankton (eggs and larvae of hake and anchovy), and their relationship with environmental features. Both ctenophore species displayed contrasting distributional patterns, associated with different physical environments, particularly temperature. M. leidyi showed a higher spatial overlap with ichthyoplankton compared to P. pileus. In addition, we found a significant negative correlation between the biomass of M. leidyi and the abundance of both fish larvae, suggesting a potential negative impact (via predation and competition) on the survival and recruitment of these 2 fisheries resources.

Vertical distribution of zooplankton groups, with an emphasis on fish larvae, in the oxygen minimum zone off southern México (December 2020)

The distribution of zooplankton groups, with an emphasis on fish larvae, in the Oxygen Minimum Zone off southern Mexico (December 2020) was analyzed. A hydrographic section of five sampling stations was made in the confluence of Transitional Water and Tropical Surface Waters. In each station, horizontal zooplankton trawls on three different dissolved oxygen conditions (~100, < 44 and < 4.4 μmol kg −1 ) were carried out by a MOCNESS net (333 μm). The 100 μmol kg −1 oxypleth (oxic condition) was ~60 m depth along the section, but the 4.4 μmol kg −1 oxypleth (suboxic) rose southward from Transitional Water (~ 150 m) to Tropical Surface Water (~ 90 m), approaching the well oxygenated layer. The distribution of the zooplankton biomass, and the most abundant zooplankton groups (e.g. copepods, chaetognaths, ostracods, euphausiids) and fish larvae showed statistically significant differences ( P < 0.01) between the oxic (100 μmol kg −1 ) and the deeper suboxic conditions. The larvae of typically dominant fish species such as the bathypelagic Vinciguerria lucetia, Diogenichthys laternatus, Diaphus pacificus and Cubiceps pauciradiatus, were present only in the oxygenated depths in the Transitional Water, and were almost absent from all depths in the Tropical Surface Water, where the oxycline shoaled. These differences in larval fish abundance were found despite little change in chlorophyll a concentration (relative units “r.u.”) along the sections, indicating that the oxycline is a limiting factor for the fish larvae. The fish larvae results contrast with previous observations from the mouth of the Gulf of California, where some species have distributions independent of water column dissolved oxygen conditions, probably as a consequence of coastal processes. Overall, our results show that even within the OMZ, variations in oxycline depth have biological implications, particularly on meroplanktonic organisms. • Transitional Water and Tropical Surface Water converge in the OMZ off southern Mexico. • The suboxic layer (< 4.4 μmol kg −1 ) is close to the oxycline in Tropical Surface Water. • The highest zooplankton abundance is in the oxic layer. • Most fish larvae are in the oxic layer in the Transitional Water. • The suboxic water elevation impacts the meroplanktonic organisms (fish larvae).

Environmental flows stimulate estuarine plankton communities by altered salinity structure and enhanced nutrient recycling

Sustainable management of estuaries depends on understanding the synergistic effects of nutrients and hydrological factors on estuarine food webs. We examined how phytoplankton, zooplankton and selected fish larval counts (Acanthopagrus butcheri, black bream) vary in relation to groundwater inputs and environmental flow releases (EFRs) in a small, highly flow-regulated estuary (Werribee, Victoria, Australia). We found that groundwater-derived nutrients and an EFR were associated with the community structure of phytoplankton and zooplankton and abundance of fish larvae. Elevated phytoplankton concentration was associated with increased flagellate abundance (genus Euglena), followed by increased abundance of diatoms (Cyclotella sp). The latter increase was primarily associated with groundwater-derived nitrate entering the estuary. Cyclotella sp. abundance collapsed following an EFR and the subsequent increase in ammonium (NH4+) concentrations in the estuary. In addition, the strong halocline and increased bottom water NH4+ concentrations resulting from the EFR appeared to stimulate population growth of flagellate taxa and calanoid copepods. The abundance of calanoid copepodites and nauplii, which are the preferred food for larval A. butcheri, greatly increased due to the EFR, and was associated with an increase in larval A. butcheri abundance at this time. This effect of the EFR on the cascading trophic interactions in the estuarine food web has rarely been shown. Our study reinforces the ecological linkages between freshwater inputs, including groundwater and riverine discharge, and estuarine biotic community structure and function. Importantly, this study underscores the potential food web consequences of freshwater flow manipulation into estuaries and provides evidence for using environmental flows to enhance and/or manage the recruitment of estuarine fishes.

Predictable hydrology, habitat and food resources determine fish recruitment dynamics in an incised tropical Australian river

Predictable hydrology, habitat and food resources determine fish recruitment dynamics in an incised tropical Australian river

Identifying drivers of tropical riverine larval fish abundance and diversity

Several hypotheses and conceptual models propose to explain mechanisms mediating riverine fish abundance, but few empirical studies to date have explored their utility in tropical systems. This study assesses key components of previous fish recruitment models by exploring spatiotemporal variation in larval fish assemblages in response to predicted key drivers in a tropical Australian river catchment. Data on larval fish composition and abundance, alongside hydrological, hydraulic, habitat and food variables, were collected monthly to bimonthly over one year at eight sites. Variables which best predicted larval fish abundance and diversity were determined with Boosted Regression Trees. The most commonly important predictors were microfauna abundance, structural habitat complexity and temperature, with high values of each predicting high larval fish abundance and diversity. Maximum larval diversity occurred when discharge was highest because several wet-season spawning taxa occurred alongside aseasonally spawning taxa. These findings support previous generic fish recruitment models, demonstrating the utility of their inclusion in the recent Riverine Recruitment Synthesis Model and the applicability of this model for describing processes important for tropical riverine fish recruitment.

Distribution, abundance, and species composition of fish larvae and juveniles of Gobiidae in the Cimaja estuary, Palabuhanratu, Indonesia

Cimaja estuary has been well known as a fishing ground for fish larvae and juveniles of amphidromous fishes. The local people call this group of fish impun and collect them frequently for consumption. However, no information about fish diversity and recruitment of amphidromous goby in the Cimaja estuary is known. Therefore, this study aims to reveal species composition, recruitment pattern, and estimation of the abundance of fish larval and juvenile amphidromous goby in the Cimaja estuary day and night. Sampling was performed monthly during the new moon period from December 2020 to February 2021. Fish specimens were identified to the lowest taxon level through a morphological approach. A total of 23,331 larvae and juveniles of Gobiidae were collected, and most of them were Sicyopterus spp. The juvenile stage (11.9-21.8 mm BL) comprised 95.6% of the catches, postflexion larvae (6.9-11.8 mm BL) contributed 3.5% to the total yield and 0.9% of the total capture consisting of flexion larvae (3.9-6.8 mm BL). Gobiid fishes are preferred to recruit and migrate into the Cimaja river during the day than at night time (p < 0.05), and their movement to the upstream are synchronized with the tidal cycle.

Temporal variation in abundance of bully sleepers (Pisces: Eleotridae) larvae and juveniles in Cisolok Estuary, Palabuhanratu Bay, Indonesia

Larvae and juveniles of bully sleepers are the primary targets for the local community surrounding Cisolok River, and this traditional fishing activity is called nyalawean. The present study aims to uncover fish larval diversity and recruitment of bully sleepers in the Cisolok river estuary. Fish sampling using a lift net was conveyed monthly from December 2020 to February 2021. Fish specimens were identified to the lowest taxon through a morphological approach and DNA Barcoding. Catch per unit effort measured the abundance of fish larvae and juveniles (CPUE, Ind.h−1). Only one species was found during the study period, namely Bunaka gyrinoides. A total of 7,353 larvae and juveniles of B. gyrinoides were captured, consisting of flexion (45 individuals; 4-5.9 mm BL), postflexion (6,887; 6-11 mm BL), and early juvenile (441; 11.1-14.8 mm BL). Postflexion larvae were the most abundant specimens, contributing 88.4-95.5%; 96-81.1%, 94.2-97.8% to the total catches in December, January, and February. Larvae and juveniles were more abundant during daylight (671-1591 Ind.h-1) rather than nighttime (147-567 Ind.h-1). These findings indicate that bully sleepers recruit and migrate upstream into the freshwater area of the Cisolok River during the day and nighttime synchronized with the tidal fluxes.

Distribution Patterns of Reef Fish Larvae in the Dipolog Srait, Philippines

The composition, abundance and distribution of reef fish were strongly influenced by the trends in salinity, temperature and mixing regimes of the water during the three oceanographic cruises conducted in the vicinity of the marine reserve networks of Dipolog Strait. Forty-seven families of reef fish larvae were identified. Carangidae, Labridae, Scaridae, Gobiidae and Apogonidae were the top five most abundant larvae comprising 64.7 % of the total number of reef fish larvae collected. Shifts in the dominance of the top five most abundant reef fish families occurred primarily between the northeast and southwest monsoons coinciding with the changes in the temperature profiles of the water column. Abundance of reef fish larvae showed variability across the three sampling periods due to the succession of the dominant species of reef fish larvae. Fluctuations in salinity brought about by the transition from Northeast to Southwest monsoon period could explain the variation. Density distribution of reef fish larvae significantly increased with the increasing depth of the mixed layer during northeast monsoon period. The downwelling off the coast of southern Negros in February and April cruises contributed to the high abundance of reef fish larvae in this part of the strait, while the uniform mixing of the water column in June 2010 at southwest monsoon resulted in the weakening of density gradient of reef fish larvae.The study demonstrated the variable responses of the reef fish larvae to the gradients of chlorophyll in the Dipolog Strait. A better understanding on the retention mechanism of reef fish larvae along the coast of southern Negros, where the main marine reserve networks exist, is provided by the present study.

Spatial Patterns of Larval and Juvenile Fish Assemblages in an Eddy Area in the Western South China Sea

The objective of this study was to investigate influence of meso-scale eddies in the western South China Sea on species composition and spatial patterns of fish larvae and juveniles based on the data collected during summer and autumn in 2012. Nintyeight species belonging to 38 families were collected, including 78 species in summer and 41 species in autumn. The dominant species in summer were Vinciguerria sp. (39.70%), Stephanolepis cirrhifer (11.21%), Caranx sp. (5.45%) and Benthosema pterotum (1.97%). The dominant species in autumn were Gobiidae sp. (15.32%), Ceratoscopelus townsendi (7.26%), Diaphus sp. (6.45%), Astronesthes sp. (5.65%) and Callionymidae sp. (4.03%). Abundance of fish larvae and juveniles in summer was higher than that found in autumn. Similarity cluster analysis results indicated that larval fish assemblages in summer can be divided into two communities: (1) larval fish in the cyclonic eddy; (2) larval fish in the anticyclonic eddies. While in autumn, the larval fish assemblages can be divided into three communities: (1) larval fish without influence of the cyclonic eddy; (2) larval fish influenced slightly by the cyclonic eddy; (3) larval fish gathered near the center of the cyclonic eddy. The variations of abundance and assemblage of larval fish might be attributed to sea surface temperature (SST), sea surface salinity (SSS) and sea level anomaly (SLA).

Species composition and density of fish eggs and larvae in the coastal waters of the South-Central Vietnam

Based on species composition and density data of fish egg and larvae in South Central coastal sea areas of Vietnam Sea waters were collected at Cù Lao Cham - Thu Bon river, Ly Son - Tra Bong river - Sa Ky river and Nha Trang - Nha Phu lagoon. Thirty-one fish eggs and larvae families were identified (about 18% of total fish eggs and 100% of wholte larvae). Cu Lao Cham - Thu Bon river has the richest species composition as 18 families, following to that is Ly Son - Tra Bong - Sa Ky and lower is Nha Trang - Nha Phu identified 15 and 10 families, respectively. The highest frequency was found in families such as Mullidae, Engraulidae and Synodontidae with 2 to 3 species (groups). The above families account for about 60% of the total number of fish eggs and larvae collected. The average fish eggs and larvae abundance about 3,630 eggs/1,000 m3 of water and 122 larvae/1,000 m3 of water. The highest eggs density is Nha Trang - Nha Phu, and the highest larvae density is Cu Lao Cham - Thu Bon river. Ly Son - Tra Bong - Sa Ky areas have eggs density lower than other areas, especially for larvae density with 22 larvae/1,000 m3 of water.

Seasonal distribution of fish larvae in mangrove-seagrass seascapes of Zanzibar (Tanzania)

Fish larvae supply in nearshore vegetated habitats, such as seagrass meadows and mangroves, contributes significantly to sustainable fish stocks. Yet, little information is available on distribution patterns of fish larvae in mangrove and seagrass habitats of the western Indian Ocean. The present study investigated the abundance, diversity and assemblage composition of fish larvae in mangrove creeks, inshore seagrass meadows (located adjacent to mangroves) and nearshore seagrass meadows (located in-between mangroves and coral reefs) in two coastal seascapes of Zanzibar (Tanzania) across seasons for 1 year. The highest mean abundances of fish larvae were recorded in mangrove creeks, while nearshore- and inshore seagrass meadows showed similar mean abundance levels. Generally, fish larvae representing 42 families were identified, with the fourteen most abundant families comprising 83% of all specimens. Fish larvae communities were dominated by specimens of the postflexion growth stage in all habitats, except in mangrove creeks in one of the two seascapes (i.e. Chwaka Bay) from April through June when abundances of the preflexion and very small-sized individuals were exceptionally high. Slightly higher fish larvae abundances were observed in mangroves during the southeast monsoon compared to the northeast monsoon, and there were also differences across months within monsoon periods for all three habitats studied. Assemblage composition of larvae did, however, not vary significantly in time or space. Our findings suggest that mangroves and seagrass meadows are highly linked shallow-water habitats with high retention of fish larvae contributing to similarity in assemblage compositions across shallow coastal seascapes. Conservation and management efforts should prioritize connected shallow-water seascapes for protection of fish larvae and to uphold sustainable coastal fisheries.

Environmental DNA detection and abundance estimates comparable to conventional methods for three freshwater larval species at a power plant discharge

AbstractEarly life stage (ELS) fishes provide a valuable metric for species, population, and ecosystem monitoring. Industrial, manufacturing, and power generating facilities in the United States can be required to monitor ELS fishes to assess impacts of facility intake waters. Traditional methods for collecting, identifying, and enumerating ELS fishes include ichthyoplankton netting and pumping from intake and discharge waters. However, sampling at these sites can prove challenging from logistical and safety standpoints, with added challenges of identifying and post‐processing of ELS fishes to quantify facility impacts on waterbodies for regulatory purposes. Methods utilizing environmental DNA (eDNA) may offer improvements in these areas. This study assessed the utility of novel, species‐specific qPCR assays to detect eDNA from three differentially abundant fish species (alewife (Alosa pseudoharengus; Wilson, 1811), gizzard shad (Dorosoma cepedianum; Lesueur, 1818), and yellow perch (Perca flavescens; Mitchill, 1814)) at the outflow of an industrial site. eDNA concentrations were compared with abundance estimates derived from two conventional collection methods to explore the potential utility of eDNA‐based methods in future monitoring. The likelihood of detecting gizzard shad, yellow perch, and alewife in the discharge waters of the power generation station was not significantly different among eDNA, plankton netting, or pump sampling. Results suggest successful detections differ by species and time of year for each method. Gizzard shad eDNA relative abundance correlated strongly with total larval abundances captured by the pumping but not the netting methods, whereas yellow perch eDNA abundance was found to correlate with both conventional methods. Alewife was not detected by any method, consistent with documentation of the decline in this species within the lake. Overall, our study found a positive relationship between eDNA abundance and larval fish abundance in both daily and seasonal sampling, suggesting that fluctuations in eDNA concentration may be linked to larval abundance.

Vertical distribution patterns of ichthyoplankton in temperate waters of New Zealand

Multifactorial sampling designs were used to determine the vertical distribution of ichthyoplankton at multiple temporal and spatial scales in New Zealand. Hypotheses concerning the vertical distribution of fish larvae were tested in the following: depth strata, surface, near-surface, mid-depth and deep, and near the substratum. The consistency of abundance patterns was examined at three sites separated by 2–20 km over 2 months. We also tested for differences in shallow water columns of two depths (20 and 40 m) and both day and night. Although peak abundance of total larval fish was found at upper and lower strata, regardless of total depth of the water column, consistent taxa specific patterns of vertical distribution were also found. Some taxa were most abundant at the surface (e.g. mullids, hemiramphids, and kyphosids), whereas others were found at multiple depths below the surface and throughout the water column, regardless of site, time or depth of water column (e.g. carangids, engraulids, clupeids, scombrids, sparids and pleuronectids). Some taxa were most abundant in shallow water columns (e.g. mullids, tripterygiids and gobiids). Rank abundance by depth stratum for non-surface dwelling species varied among sites and times. Diel vertical movements were detected, some taxa (e.g. clupeids, scombrids and bothids) that were most abundant at the surface at night whereas for other taxa this pattern was more variable (e.g. carangids). We conclude that diel depth-related patterns in shallow water columns will influence interactions among taxa and the importance of different transport mechanisms for larval transport.

Ichthyoplankton Species Composition and Assemblages From the Estuary to the Hukou Section of the Changjiang River

Estuary river–lake (ERL) complex is critical for the development of ichthyoplankton, which plays an essential role in the breeding, nursing, and recruitment of freshwater fish species. In this study, different ERL sections were selected to investigate the ichthyoplankton assemblage from the Changjiang River estuary to its Hukou section between May 2018 and August 2020. During the study period, fish larvae of 40, 35, 54, and 46 fish species were sampled in the Rugao (RG), Nanjing (NJ) (nearby estuary), Anqing (AQ), and Hukou (HK) (connected river–lake) sections in the Changjiang River, respectively. Results on ichthyoplankton surveys revealed fluctuating assemblage patterns in the different river sections; larval fish species composition presented ecological habitat-dependent characteristics, which supported the importance of ERL complex for ichthyoplankton development. Furthermore, the density of fish larvae was negatively correlated with water transparency but positively correlated with water temperature, the daily rate of water level increase, and runoff in the limitative range. A generalized additive model analysis indicated that the hydrological factors significantly affecting larval fish abundance are water temperature, transparency, the daily rate of water level increase, and runoff (p &amp;lt; 0.05). These results also indicated that river estuaries and river–lake connected complexes are essential for ichthyoplankton recruitment and migration. In combination with the historical record, ichthyoplankton assemblage’s patterns in the Changjiang River lower reaches were preliminarily elucidated, although additional works are needed such as assessing effects on their survival and recruitment.

Assemblage Structure of Larval Fishes in Epipelagic and Mesopelagic Waters of the Northern Gulf of Mexico

The early life stages of fishes play a critical role in pelagic food webs and oceanic carbon cycling, yet little is known about the taxonomic composition and distribution of larval fishes in the northern Gulf of Mexico (GOM) below the epipelagic (&amp;lt;200 m). Here, we provide the first large-scale characterization of larval fish assemblages in the GOM across epipelagic, mesopelagic, and bathypelagic regions (0–1,500 m), using samples collected during the Natural Resource Damage Assessment conducted following the Deepwater Horizon oil spill (DWHOS). These data contain &amp;gt; 130,000 ichthyoplankton specimens from depth-discrete plankton samples collected across 48 stations in the GOM during six cruises conducted in 2010 and 2011. We examined indices of abundance and diversity, and used a multivariate regression tree approach to model the relationship between larval fish assemblages and environmental conditions. The total abundance of larval fish followed a generally decreasing trend with increasing depth, and family-level richness and diversity were significantly higher in the epipelagic than mesopelagic and bathypelagic regions. Fourteen distinct assemblage groups were identified within the epipelagic, with depth, surface salinity, and season contributing to the major branches separating groups. Within the mesopelagic, seven distinct assemblage groups were identified and were largely explained by variation in depth, season, and surface temperature. Bathypelagic assemblages were poorly described by environmental conditions. The most common epipelagic assemblage groups were widely distributed across the GOM, as were all mesopelagic assemblage groups, suggesting limited horizontal structuring of GOM larval fishes. Of the mesopelagic-associated fish taxa, four dominant families (Myctophidae, Gonostomatidae, Sternoptychidae, Phosichthyidae) comprised the majority of the catch in both the epipelagic (63%) and combined mesopelagic and bathypelagic (97%) regions. Dufrêne-Legendre indicator analysis confirmed that these dominant families were characteristic of epipelagic and mesopelagic assemblages; the larvae of less common mesopelagic-associated families largely identified with epipelagic assemblage groups. A lack of baseline data about the distribution patterns of early life stages of mesopelagic fishes in the GOM was apparent following the DWHOS, and these findings provide a valuable reference point in the face of future ecosystem stressors.

Precision of larval herring abundance and body length assessments when sampling with BONGO nets for spawning site mapping

Data on the abundance and size structure of larval and juvenile fish are commonly used in environmental research. Knowledge about the repeatability of the results of a given sampling tool is an important part of planning sample collection schedules. The aim of this research was to evaluate the variance in the abundance and length of herring larvae (6.9–24.4 mm SL) collected with 505 bongo nets during 12 cruises conducted during April-June at 6–9 stations in the Pomeranian Bay, Baltic Sea, from 2015 to 2018. The differences (mean value of % deviation from the mean) between the left and right bongo nets (compared during 17 tows) were 21.6% for larval abundance and 3.6% for the SL measurement. When three tows were subsequently conducted at the same station (compared at 6 stations), the differences were 19.7% and 10.1% for abundance and the SL assessment, respectively. When samples were collected at the same stations on consecutive days (compared for 75 paired days), the error was 33.4% for abundance and 6.1% for SL. Several factors (filtered-water volume, larval abundance, larval size, wind strength, and station location) were tested for their effect on the magnitude of the variations, but only sampled larvae abundance was found to be significant with lower precision for low abundance. Although the above low precision level did not significantly affect the overall assessment of larval abundance and SL within the investigated geographical area within a given year, it should be considered that differences of ca. ± 10% (for SL) and ca. ± 33% (for abundance) are within the sampling method errors, which correspond to ca. thirteen percent (for SL) and 200% (for abundance) of the absolute differences expressed as % of the lower value. While the present results were obtained for herring, we believe that the conclusions are also applicable to early life stages of other fish species, especially clupeids such as sprat, menhaden, and smelt.

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.

Water masses and larval fish habitats in the Pacific tropical-subtropical convergence off Mexico

In early summer (June 2010), we used zooplankton and hydrographic sampling to analyze relationships between larval fish habitats and converging water masses in the Pacific tropical-subtropical region off Mexico. Results showed an equatorward jet parallel to the Baja California Peninsula (the Tropical Branch of California Current) which was located northward of 25oC surface isotherm. In this area, a larval fish habitat indicated by Triphoturus mexicanus larvae was identified. The habitat had low larval abundance (17 larvae per 10 m2) with major larval concentration below the thermocline (∼ 20 Co and oligotrophic conditions, < 0.3 mg m-3). Two larval fish habitats were defined south of the 25oC surface isotherm. One larval fish habitat was located in a coastal jet and cyclonic field immersed in the Transitional Waters, with the highest larval fish abundance (49 larvae 10 per m2). The indicator species were Vinciguerria lucetia and Diogenichthys laternatus. Both species had the greatest abundance in the warm (∼25 oC) and mesotrophic (>1 mg m-3) waters of the shallow thermocline (∼30 m depth). The other larval fish habitat occupied an area of anticyclonic circulation in the offshore California Current Water, where the thermocline was depressed ∼ 70 m depth. Oligotrophic conditions (0.3 mg m-3) corresponded with the lowest mean larval abundance (14 larvae per 10 m2) of the study. The distribution of the larval fish habitats and their indicator species correspond with the water masses distributions in the Tropical-Subtropical convergence, which are modulated by mesoscale structures affecting the thermocline depth and the larval life-history.