Fate of coastal fish larvae transported to offshore waters: lost at sea or recruits?

HERZKA, SHARON Z.; COMPAIRE, JESUS C.; PÉREZ-BRUNIUS, PAULA; PALMA-GALINDO, IBRAHIM; VALENCIA-MÉNDEZ, OMAR

Portland, Oregon

Conferencia; 27 Conferencia Bianual de la Coastal and Estuarine Research Federation (CERF 2023); 2023

The presence of fish larvae of adults that occupy coastal-neritic habitats has been repeatedly observed in the Gulf of Mexico's (GM) deep-water region (depth > 1000 m). Their transport to offshore waters may represent a loss of potential recruits, or regional circulation could deliver them to suitable juvenile recruitment habitats. We examine the distribution of coastal and neritic fish larvae throughout the deep-water region of the central and southern GM during three oceanographic cruises (XIXIMI-04, 05 and 06) held during the summers of 2015, 2016, and 2017. Zooplankton biomass and larval densities of coastal and neritic species were higher in the oceanic waters of the Bay of Campeche (BofC) compared to the central, oligotrophic Gulf. This is consistent with the previously documented offshore transport of river inflow and shelf waters. Gobiidae larvae, whose adults occupy estuarine, coastal, or shallow reef habitats, were selected for a more detailed study. The larval density of the two most abundant genera of Gobiids ( Ctenogobius and Coryphopterus)indicates offshore transport during the three cruises, particularly within the BoC. The probable origin of larvae of the two genera was inferred through numerical modeling experiments using HyCOM and surface chlorophyll maps. The five stations with the highest densities of Ctenogobius and Coryphopterus were seeded with 20,000 particles at seven depths (0-200 m) and tracked backward in time for 15 and 35 days to infer larval origin. Five coastal provinces of probable origin were defined, spanning the shelves of Tamaulipas, Veracruz, Tabasco, Campeche, and Yucatan, Mexico. The highest larval contribution during the three cruises was from the coastal province of Veracruz. Their offshore dispersal is likely due to the interaction of the Campeche cyclonic gyre with the southward circulation over the thin shelf and slope off Veracruz and convergent circulation along the southern shelf. No transport was detected from the central and eastern Yucatan shelf to the BofC, suggesting limited connectivity. Particle transport experiments will also be applied to examine whether there are transport processes that may deliver the larvae to the shelf and coast. Determining whether the larvae of coastal and neritic fish species can recruit to suitable nursery habitats following their transport to offshore waters is central to understanding their recruitment and population dynamics