Abstract¡G The principal objectives of this research are to investigate the species composition and distribution of larval fish in relation to water temperature¡Bsalinity¡Bchlorophyll a and the abundance of copepods in Tapeng Bay and Kaoping coastal waters. Thirty-one species of the larval fish belonging to 29 genera and 16 families were identified in Tapeng Bay, with the mean numerical abundance of 22.9 ¡Ó40.7 ind./100m3 during the sampling period between June 1999 and December 2001. The trend of seasonal change in numerical abundance of the larval fish was not coincident interannually. The 7 most dominant species were Omobranchus sp., Tridentiger obscurus, Pterogobius Zonoleucus, Blenniidae gen. sp., Gobiidae gen. sp., Entomacrodus lighti and Engraulis japonicus, occupied 94% of the total larval fish abundance¡Famong these, the first two dominant species, Omobranchus sp. and T. obscurus contributed to 80% of the total count. One hundrad and eighty-four species of the larval fish belonging to 130 genera and 69 families were identified in Kaoping coastal waters, with the mean numerical abundance of 390.6¡Ó593.5 ind./100m3 during the sampling period between June 1999 and June 2001. Generally, the numerical abundance of the larval fish showed significantly seasonal changes, with lowest in winter and up to highest value in summer. The 10 most dominant species were Sillago japonica, Engraulis japonicus, Tridentiger obscurus, Gobiidae gen. spp., Pagrus major, Scomberoides lysan, Leiognathus nuchalis, Ceratoscopelus warmingi, Scatophagus argus and Diogenichthys laternatus, occupied 67% of the total larval fish abundance. The mean abundance, species number and species diversity index of the larval fish were obvious higher in Kaoping coastal waters than in Tapeng Bay. The dominant species of larval fish in Tapeng Bay were mostly sandy benthic species (Blenniidae and Gobiidae) and coastal epipelagic species (Engraulidae). The larval fish assemblage in Kaoping coastal waters was diverse, and dominated by benthic species (Sillaginidae), sandy bottom species (Blenniidae and Gobiidae), coastal epipelagic species (Engraulidae), mesopelagic species (Myctophidae) and coastal-migrant species (Scatophagidae).

The objective of this dissertation was to examine sailfish (Istiophorus platypterus) and blue marlin (Makaira nigricans) spawning in the Straits of Florida, with a specific focus on 1) the physical and biological characteristics of the spawning environment, and 2) the role of the region within the broader spawning patterns of these two species. In order to accomplish these objectives, two years of monthly ichthyoplankton collections and physical measurements across the Straits of Florida were combined with a finer-scale Lagrangian study. Additionally, a molecular species-identification methodology was developed that was both high-throughput and suitable for use with a broad taxonomic range of species. An initial analysis considered the diversity, assemblages and associated habitat of the larvae of large and medium size pelagic species. In total 36 species and 14,295 individuals were collected during this study, with the highest diversity occurring during the summer, and in the western frontal region of the Florida Current. Sailfish were included in an assemblage with Auxis rochei, A. thazard and Euthynnus alleterattus, all species found in highest abundance during the summer along the western edge of the Straits of Florida. Blue marlin grouped most closely with Thunnus atlanticus, Ruvettus pretiosus and Lampris guttatus, all summer spawners, whose larvae tended to occur further offshore. The primary environmental factors associated with these assemblages were SST (highest summer-early fall), day-length (highest early summer), thermocline depth (shallowest on the Florida side) and fluorescence (highest on the Florida side). A Lagrangian sampling effort was then used to more specifically evaluate the role of frontal zones in sailfish spawning. The results of this sampling indicated that the highest levels of sailfish spawning occurred in a frontal zone associated with the formation of a submesoscale frontal eddy. This spawning resulted in the first-feeding larvae occupying an area rich in prey items. Given the small spatial-scale of the front, and the distribution of the eggs of adult prey items, the results of this work would suggest that sailfish are actively targeting features for spawning that are favorable to the growth and survival of their larvae. Finally the relative importance of the Straits of Florida as a spawning ground was evaluated by calculating the annual egg production of both sailfish and blue marlin within this region. In total it was estimated that 2.1% of western Atlantic sailfish spawning and 1.6% of Atlantic wide blue marlin spawning occurs in the SF. Pop-up satellite tags deployed on sailfish at the start of the spawning season revealed their short residency times in the SF, suggesting that a large (≈10%) transient portion of the sailfish population is responsible for the SF egg production. These results indicate that the SF is a migratory bottleneck for sailfish. In conclusion the results of this study indicate that a hierarchy of physical and biological processes influence the distribution of billfish spawning in space and time. The results provide insights into the movement patterns and life history strategies of these species, and ultimately may aid in the development of the spatially explicit ecosystem based management approaches that are currently being advocated.

¡@¡@The main objectives of this study is to: (1) understand the recruitment pattern and mechanisms of fish larvae in the kenting waters, such as seasonal variation, distance from shoreline, depth, and diurnal migration of the assemblages of larvae fish. The correlation of the tempo-spatial variations of larval fish communities with temperature, salinity, and chlorophyll were also investigated; (2) to apply DNA barcode technique to identify fish larvae to lower taxonomic categories so as to reveal the temporal or spatial variation of the community structure of fish larvae that was unclear if the identification could only up to higher level. Additionally, DNA barcoding can help us to compile the diagnostic keys for larval fish species identifications. ¡@¡@For fish larval communities studies, fish larvae were collected from four seasons and two different depths during 2001-2002, and every two hours in a day during 10-11 April 2004 by the standard ORI net in Kenting. 527 specimens belonging to 86 taxa and 51 families of fish larvae were collected during 2001-2002. Randomization tests show significant differences between fish larval abundance vs. depths, and the number of families vs. seasons. Canonical correspondence analysis (CCA) shows that temperature and salinity were the main environmental factors, and chlorophyll was the second. 158 specimens belonging to 44 taxa and 34 families of fish larvae were collected during 24 hour survey. The abundance and diversity of fish larvae increase after sunset, and reach to their climax in the midnight. ¡@¡@For COI species identification, 1,505 of the post-flexion stage fish larvae specimens belong to 44 taxa and 34 families were collected by the four-time surveys of light trap in Kenting coral reef area during 2005-2007. Fifteen types of damaselfish larvae and five types of butterflyfish larvae were identified based on their morphological characters. The COI were used to identify the morphological types of damselfishes and butterflyfishes to species level. Fifteen morphological types of damselfishes (Pomacentridae) can be identified to 11 species and three genera. Five morphological types of butterflyfishes (Chaetodontidae) can be assigned to four species and one genus. After COI identification to the lower taxonomic levels, the ordination analysis can clearly reveal the seasonal variation. The result shows that applying DNA barcode technique to identify fish larvae to lower taxonomic categories indeed can reveal temporal or spatial variation of the community structure of fish larvae.

No description available.

Larval fish assemblages were investigated during a three-year multidisciplinary project conducted off the coast of south-western Australia. Larvae were sampled using replicated oblique bongo net tows along a five-station transect extending from inshore (18m depth) to offshore waters (1000m depth). A total of 148 taxa from 93 teleost families were identified. Larvae of Gobiidae, and Blenniidae were abundant inshore, while larvae of pelagic and reef-dwelling families, such as Clupeidae, Engraulidae, Carangidae and Labridae were common in continental shelf waters. Larvae of oceanic families, particularly Myctophidae, Phosichthydae and Gonostomatidae, dominated offshore assemblages. Inshore larval fish assemblages were the most seasonal, in terms of species composition and abundance, with offshore assemblages the least so. Multivariate statistical analyses revealed larval fish assemblages to have a strong temporal and spatial structure. Assemblages were closely correlated to water masses, with species distributions reflecting both cross shelf and along-shore oceanographic processes and events. The strength and position of the warm, southward flowing Leeuwin Current, and of the cool, seasonal, northward flowing Capes Current were shown to drive much of the variability in the marine environment, and thus larval fish assemblages. Many of the distinctions between larval fish assemblages on the continental shelf were attributable to patterns of abundance in clupeiform larvae. While larvae of Engraulis australis and Spratelloides robustus showed clear seasonal and spatial distribution patterns, larvae of Sardinops sagax and Etrumeus teres were found throughout the year, with high interannual variability in abundance. Abundances of larvae from all pelagic clupeiform species were negatively correlated to microzooplankton concentrations. Peaks of abundance of S. sagax and E. teres, in particular, appeared to be better aligned with favourable transport and retention conditions. A detailed comparison of the horizontal and vertical distribution of larval fishes highlighted the influence of contrasting oceanographic conditions between summer and winter on larval fish assemblages. Although most fish larvae were found above the thermocline, depth distributions differed between taxa, and were shown to influence their offshore transport. Neustonic fish larvae showed potential for significant dispersion during summer, as a result of offshore Ekman transport. Mesoscale Leeuwin Current eddies were a feature of the oceanography of the region, and their influence on larval fish assemblages was examined in both an anti-cyclonic eddy (warm-core) and a cyclonic eddy (cold-core). The warm-core eddy contained larval fish assemblages that were distinct from those in the cold-core eddy, with lower larval fish concentrations, especially in the eddy centre. Although the eddies originated near the continental shelf, larval fish assemblages within both eddies were largely oceanic, probably a result of the age of the eddies when they were sampled (about 5 months). Overall, larval fish assemblages showed strong temporal and spatial structure, and were well aligned to water masses in the region. The unique oceanography off south western Australia thus has considerable implications for both larval fish transport, and potential recruitment to regional fisheries.

Anglers unlawfully introduced gizzard shad Dorosoma cepedianum into Claytor Lake, Virginia in the late 1980s, apparently with the intention of improving the sportfishery by adding an additional clupeid prey resource. This study examined the trophic interactions between larval shad and resident zooplanktivorous fishes, in an attempt to discover the potential for trophic competition and negative impacts to these fish species. Ichthyoplankton sampling in 1997 and 1998 showed that peak abundances of larval shad overlapped temporally and spatially with both larval Lepomis spp. and larval alewife Alosa pseudoharengus. Peak larval shad density (0.04-0.06 fish/m3) was two to three orders of magnitude less than that reported from other reservoir systems, slightly less than that of larval alewife in Claytor Lake (0.05-0.07 fish/m3), and significantly less than that of larval Lepomis spp. in Claytor Lake (0.28-0.51 fish/m3). Diet overlap values indicated potential resource overlap among all three larval taxa. Diet of larval shad did not overlap with that of either age-0 Micropterus spp. or adult alewife. All species of limnetic larvae examined showed feeding preferences for Diaphanosoma and copepod nauplii. Crustacean zooplankton densities did not respond negatively to peak larval fish abundances, and never dropped below 250-400 organisms/L. In Claytor Lake, the impact of trophic competition with larval gizzard shad on other zooplanktivores currently appears to be minimized by low densities of larval shad and abundant crustacean zooplankton. / Master of Science

In the Beaufort Sea, freshwater input from the Mackenzie River creates a relatively warm and turbid plume across the coastal shelf region. To determine the effects of the Mackenzie River plume on marine larval fish abundance, distribution and assemblages; this study sampled larval fish by using 500 μm bongo nets and obtaining oceanographic measurements across the plume gradient during July and August of 2007. Three larval fish assemblages were identified within three water masses: the intense plume assemblage was dominated by Pacific herring (Clupea pallasii pallasii), the diffuse plume assemblage was dominated by the sub-family Lumpeninae and the oceanic assemblage was dominated by Arctic cod (Boreogadus saida). Also, results revealed that there were no significant differences in the total larval fish abundances within these water masses. In conclusion, this study suggests that the Mackenzie River plume might be identified as an Ecologically and Biologically Significant Area (EBSA), based on the uniqueness criteria under Canada’s coastal conservation strategy.

In the Beaufort Sea, freshwater input from the Mackenzie River creates a relatively warm and turbid plume across the coastal shelf region. To determine the effects of the Mackenzie River plume on marine larval fish abundance, distribution and assemblages; this study sampled larval fish by using 500 μm bongo nets and obtaining oceanographic measurements across the plume gradient during July and August of 2007. Three larval fish assemblages were identified within three water masses: the intense plume assemblage was dominated by Pacific herring (Clupea pallasii pallasii), the diffuse plume assemblage was dominated by the sub-family Lumpeninae and the oceanic assemblage was dominated by Arctic cod (Boreogadus saida). Also, results revealed that there were no significant differences in the total larval fish abundances within these water masses. In conclusion, this study suggests that the Mackenzie River plume might be identified as an Ecologically and Biologically Significant Area (EBSA), based on the uniqueness criteria under Canada’s coastal conservation strategy.

Essential fatty acids are necessary for growth, survival, and development of larval fishes, but there is limited information on the essential fatty acid requirements of larval southern flounder (Paralichthys lethostigma). The objectives of this study were to elucidate connections between dietary supply of docosahexaenoic acid (DHA) and arachidonic acid (ARA) and deposited fatty acids in the head or body, and then link diet and stored fatty acids in the head or body with larval quality traits. From 4-15 days posthatch (dph), southern flounder larvae were fed rotifers enriched with four different combinations of DHA-rich Algamac 3050 and ARA-rich Algamac ARA. Fatty acid concentrations in the head and body were measured at 15 dph, and relationships between fatty acids in head or body and in the diet were determined. Larval quality traits, including specific growth rate (SGR), survival, and eight behavioral performance variables were measured. Results showed that concentrations of DHA and ARA in the head and in the body were correlated with concentrations of DHA and ARA in the diet. Growth rate did not vary among the four diets, but survival was positively correlated with the amount of lipid in the diet. Responsiveness to a visual stimulus was positively correlated with the concentration of DHA in the diet, the ratio DHA:EPA in the head, and total energy content of the diet. Turning rate during routine swimming was correlated with body DHA. This study demonstrates the influence of DHA content, total lipid content, and energy levels in the diet of southern flounder and provides a foundation for future studies examining causal factors of recruitment variability or larviculture production success. / text

The processes influencing larval fish survival in the low-latitude open ocean are poorly understood, especially with regard to feeding. As part of a large-scale study that included two years of monthly sampling in the Straits of Florida (SOF), the objectives of this dissertation were to elucidate the larval fish feeding behaviors and strategies of 1) istiophorid billfishes, 2) tunas, and 3) coral reef fishes, while also 4) characterizing the feeding environment, synthesizing the dominant trophic pathways to fish larvae, and reviewing the literature for evidence of latitudinal distinctions in larval fish trophodynamics. Larval billfishes exhibited highly selective feeding, and their diets were numerically dominated (90%) by two genera of crustaceans, Farranula copepods and Evadne cladocerans. These prey were consumed throughout early larval ontogeny, from first-feeding through piscivorous lengths (> 5 mm), until piscivory became exclusive near 12 mm. High feeding incidence (0.94) and rapid digestion (~3.5 hrs) suggests frequent and successful feeding by billfish larvae. For tunas, nearly all larvae examined (>98%) contained prey. Thunnus spp. exhibited a mixed diet, while skipjack, little tunny, and Auxis spp. nearly exclusively consumed appendicularians. All four tuna taxa co-occurred in the western SOF where prey was more abundant, while in the central and eastern SOF (where prey availability was lower), only Thunnus spp. and skipjack were present. Additionally, these two taxa exhibited significantly different vertical distributions. Estimates of predatory impact indicated the potential for depletion of resources in the absence of the spatial and dietary niches of larval tunas. Coral reef fish families examined included Serranidae, Lutjanidae, Mullidae, Pomacentridae, Labridae, Scaridae, and Acanthuridae. Feeding incidences were high (0.94 to 1.0) for all taxa except scarids (0.04), and diets were narrow and predator-specific. Cluster analysis yielded clear groupings based on the selective feeding exhibited by the taxa, while within taxa, canonical correspondence analysis illustrated the change in diet with a variety of variables. The physical and biological environment varied markedly across the SOF, largely influenced by the Florida Current. Characteristics examined included thermocline depth, fluorescence, and abundances of total plankton and copepod nauplii. The feeding ecologies of the 21 taxa of fish larvae in this work were synthesized into qualitative and quantitative webs that illustrate the variable trophodynamic strategies of larvae in the SOF and the levels of community reliance upon zooplankton prey types. A review of 170 investigations on larval fish feeding revealed notable distinctions between high- and low-latitude regions, highlighting the substantial variability across environments in the role of larval fishes within the planktonic food web.