A comprehensive biochemical characterization of settlement stage leptocephalus larvae of bonefish (Albula vulpes)

A Comprehensive Biochemical Characterization of Hybrid Grouper Larvae (Epinephelus fuscoguttatus♀ × Epinephelus lanceolatus♂) during Yolk-Sac Larval Development

To investigate the shifts in the biochemical composition of hybrid grouper during the early larval stages, we collected samples at various developmental milestones, spanning from newly hatched larvae (stage I) to 4 days after hatching (stage V). Our findings revealed several notable trends: (1) The total length of hybrid grouper larvae exhibited a significant increase as the yolk-sac absorption progressed from stage I to V. Concurrently, there was a marked decrease in yolk volume and oil volume during the transition from stage I to III, followed by a gradual decline from stage III to V. (2) Dry weight and total lipid content displayed a rapid reduction throughout the larval development period, while the total protein content exhibited a declining trend. (3) The concentrations of triacylglycerols and wax esters/steryl esters decreased considerably, particularly at stage V. However, no differences were observed among the contents of ketones, hydrocarbons, and sterols. (4) As yolk-sac larvae developed from stage I to V, a significant reduction was observed in the levels of essential amino acids (EAAs), such as leucine, valine, isoleucine, phenylalanine, glycine, alanine, serine, proline, and tyrosine. This trend was also observed for non-EAAs and total amino acids, with fluctuations in the content of other amino acids. (5) There was a significant decrease in the levels of specific fatty acids, including C16:0, saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs), C18:0, 18:1n-9, and C20:4n-6. In contrast, the contents of C22:6n-3, polyunsaturated fatty acids (PUFAs), n-3 PUFA, n-6 PUFA, and the combination of docosahexaenoic acid (DHA) + eicosapentaenoic acid (EPA), as well as the DHA/EPA ratio, remained stable from stage I to III but declined thereafter. (6) During the early developmental stages, the utilization sequence of fatty acids followed a pattern of prioritizing SFAs, followed by MUFAs, n-6 PUFA, and n-3 PUFA. These findings provide further insights into the nutritional priorities of hybrid grouper larvae during their early development, with a particular emphasis on lipids and fatty acids as vital energy sources. Additionally, our results highlight variations in the efficiency of utilization among different types of fatty acids, while protein utilization remained relatively stable, characterized by the selective consumption of amino acid content.

Biophysical larval dispersal models of observed bonefish (Albula vulpes) spawning events in Abaco, The Bahamas: An assessment of population connectivity and ocean dynamics

Biophysical models are a powerful tool for assessing population connectivity of marine organisms that broadcast spawn. Albula vulpes is a species of bonefish that is an economically and culturally important sportfish found throughout the Caribbean and that exhibits genetic connectivity among geographically distant populations. We created ontogenetically relevant biophysical models for bonefish larval dispersal based upon multiple observed spawning events in Abaco, The Bahamas in 2013, 2018, and 2019. Biological parameterizations were informed through active acoustic telemetry, CTD casts, captive larval rearing, and field collections of related albulids and anguillids. Ocean conditions were derived from the Regional Navy Coastal Ocean Model American Seas dataset. Each spawning event was simulated 100 times using the program Ichthyop. Ten-thousand particles were released at observed and putative spawning locations and were allowed to disperse for the full 71-day pelagic larval duration for A. vulpes. Settlement densities in defined settlement zones were assessed along with interactions with oceanographic features. The prevailing Northern dispersal paradigm exhibited strong connectivity with Grand Bahama, the Berry Islands, Andros, and self-recruitment to lower and upper Abaco. Ephemeral gyres and flow direction within Northwest and Northeast Providence Channels were shown to have important roles in larval retention to the Bahamian Archipelago. Larval development environments for larvae settling upon different islands showed few differences and dispersal was closely associated with the thermocline. Settlement patterns informed the suggestion for expansion of conservation parks in Grand Bahama, Abaco, and Andros, and the creation of a parks in Eleuthera and the Berry Islands to protect fisheries. Further observation of spawning events and the creation of biophysical models will help to maximize protection for bonefish spawning locations and nursery habitat, and may help to predict year-class strength for bonefish stocks throughout the Greater Caribbean.