Distribution and densities of fish larvae species with contrasting life histories as a function of oceanographic variables in the deep-water region of the southern Gulf of Mexico

Abstract

We describe the larval occurrence and density of six fish species with contrasting life histories and examine their relationships with oceanographic variables during two seasons in the deep-water region (> 1000 m) of the southern Gulf of Mexico based on 12 cruises (2011–2018). Given that Caranx crysos adults are neritic, larval presence close to the continental shelf indicates offshore cross-shelf transport to oceanic waters, which likely leads to mortality. Generalized additive models indicated that C. crysos density was not related with oceanographic variables, while Auxis spp. (with neritic and oceanic adults) was related to wind speed, sea surface temperature, sea surface height, and surface chlorophyll a. The mesopelagic Benthosema suborbitale, Notolychnus valdiviae and Bregmaceros atlanticus were more abundant and broadly distributed, and higher density was found in conditions indicative of higher nutrient availability and productivity, suggesting greater feeding success and survival. The distribution of the epi- and mesopelagic Cubiceps pauciradiatus extended through the southern Gulf of Mexico, and was related to wind speed, sea surface temperature, stratification and chlorophyll a. Our results suggest that the density of the neritic species in oceanic waters could be mediated by regional cross-shelf transport, while for oceanic species is linked with productivity.

Assemblage Structure of Ichthyoplankton Communities in the Southern Adriatic Sea (Eastern Mediterranean)

“…Environmental factors, in fact, strongly influence the distribution of ichthyoplankton, which are an important component of marine plankton communities in the oceanic ecosystem, playing a key role in the marine food webs through bottom-up control [31]. It is important to understand how connectivity can influence survival during the early life developmental stages [4]. The adult fish populations are connected to the survival and successful recruitment through time of the early life stages (eggs, larvae and juveniles) [32].…”

“…It is already known that the spawning period for some fish larval species precedes plankton blooms [35]. Fish larvae, due to weak swimming ability, are passively moved long distances horizontally, perhaps even for hundreds of kilometres [4,34], as a result of various environmental conditions. The space-time variability of oceanographic structures can influence the physiology and behaviour of ichthyoplankton, leading to variations in recruitment and survival [36].…”

“…Larval fish assemblages belong to the meroplankton community, and their abundance and composition are linked to the reproductive cycles of the adult fish. Marine fish larvae can be classified depending on habitat and the depth of the areas in which the adults live and spawn [2][3][4]. Coastal species are found from the coastline to the edge of the continental shelf (above 200 m depth), and their spawning period is spring/summer.…”

“…Coastal species are found from the coastline to the edge of the continental shelf (above 200 m depth), and their spawning period is spring/summer. Spawning occurs in superficial layers or in shallow demersal habitats, and larvae produced are carried to deeper oceanic waters [4][5][6][7]. Species inhabiting the pelagic waters can be classified according to the layer in which they live: epipelagic (0-200 m), mesopelagic (200-1000 m) and bathypelagic (1000-4000 m).…”

“…Species inhabiting the pelagic waters can be classified according to the layer in which they live: epipelagic (0-200 m), mesopelagic (200-1000 m) and bathypelagic (1000-4000 m). The spawning period is different for epipelagic and mesoor bathypelagic species; the former spawn between spring and summer, while the latter spawn throughout the year, mainly above 500 m, although some species show one or two spawning peaks [3,4,8].…”