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More than half of the fish biomass of coastal rocky reefs depends on zooplankton; however, the trophic basis of estuarine fish assemblages remains unknown. We quantified the trophic basis (i.e. basal energy sources) of fish community biomass inhabiting three habitat types (seagrass, natural reef and artificial reef) in two estuaries, compared with two coastal rocky reef sites. Fish assemblages were surveyed with Baited Remote Underwater Video (BRUVs) and the species abundance, richness and biomass of fish were classified into nine functional feeding groups (6 teleost and 3 elasmobranch). Comparable metrics for coastal fish assemblages were obtained from published surveys using BRUVs. Using the functional feeding group biomass and the group-specific diet composition, the breakdown of energy sources was calculated using a food web analysis. Estuarine reef habitats had different species and different functional feeding group composition than seagrass habitat. The majority of fish biomass in the seagrass habitat was supported by detritus (51% in Botany Bay) or macrophytes (58% in Lake Macquarie). In contrast, zooplankton supported most fish biomass (45-59%) at the coastal reef locations, and in reef habitat in one estuary (35-43%), but not the other estuary (33-34%). Trophic pathways which support fish assemblages, are key in identifying mitigation measures which can help conserve these populations with growing urbanisation of estuaries and coasts., Author(s): Belinda K. Goddard [sup.1] , Alistair Becker [sup.2] , David Harasti [sup.2] , James A. Smith [sup.1] [sup.3] , Roshni C. Subramaniam [sup.4] , Iain M. Suthers [sup.1] [sup.4] [...]

Mesopelagic fishes are important consumers of zooplankton and are the prey of oceanic predators. Some mesopelagic fishes (e.g., Myctophidae) undertake a diel vertical migration where they ascend to the near-surface waters during the night to feed and descend into the depths during the day to avoid predators. Other mesopelagic fishes (e.g., Sternoptyx) remain at depth throughout the day. Although fishes of different depths eat different prey items, vertical migration likely leads to overlap in species distributions and diet, potentially linking trophically transmitted surface and deep-pelagic parasite communities. The study of gut contents and parasites can yield insights into the trophic dynamics occurring within these assemblages. We examined the diet and parasite assemblages of 18 mesopelagic fish species in the Gulf of Mexico. We identified six different feeding guilds within this assemblage based on gut contents: copepods, copepods/mesozooplankton, copepods/ostracods, gelatinous zooplankton, generalist mesozooplankton, and upper-trophic level items such as fish. Although parasite abundances were generally low, mesopelagic fishes hosted a diverse assemblage of parasites, including larval and adult digeneans, larval cestodes, larval nematodes, and larval acanthocephalans. The parasite assemblages differed significantly among host feeding guilds. Large, vertically migrating fishes that predate upon fish and squid communities had a greater likelihood of having one or more parasites compared to the other fishes examined. Results from this study suggest that upper-trophic level mesopelagic fishes are more regularly involved in the life cycle of parasites in the Gulf of Mexico than zooplanktivorous fishes., Author(s): Matthew S. Woodstock [sup.1] , Christopher A. Blanar [sup.2] , Tracey T. Sutton [sup.1] Author Affiliations: (1) grid.261241.2, 0000 0001 2168 8324, Department of Marine and Environmental Sciences, Halmos [...]

Arctic marine food webs are centered on polar cod (Boreogadus saida), a small, largely pelagic gadid, which movement and migration remain unclear, especially for the early life stages. The present study examined the otolith chemistry of juvenile polar cod from six oceanographic regions of the Arctic Ocean in order to document patterns of spatial segregation, dispersion and migration during the species early life. The freshwater winter refuge hypothesis, suggesting that polar cod larvae start to hatch in winter in freshwater-influenced regions but only later in the season in purely marine regions, was also tested. Five elemental ratios (Li/Ca, Mg/Ca, Mn/Ca, Sr/Ca and Ba/Ca) were analyzed by laser ablation inductively coupled plasma mass spectrometry in three otolith zones representing the egg, larval and juvenile stages. The concentration of each of the five elements at the edge of the otoliths, corresponding to incorporation shortly before capture, was significantly correlated with surface salinity and temperature at capture site and date. Otolith chemistry differed between juveniles from freshwater-influenced regions (Laptev Sea, Hudson Bay Amundsen Gulf) and those from purely marine regions (Lancaster Sound, Baffin Bay, Frobisher Bay), in agreement with dissolved concentrations of at least some of the target elements in the Arctic Ocean. Discriminant function analyses including all five elements provided valuable information on the species population structure and dispersion of early stages. The correspondence between otolith Mn/Ca, Ba/Ca and vertical profiles of dissolved Mn and Ba in the water column may reflect the ontogenetic vertical migration of juvenile polar cod in late-summer and fall., Author(s): Caroline Bouchard[sup.1] , Simon R. Thorrold[sup.2] , Louis Fortier[sup.1] Author Affiliations: (1) Quebec-Ocean, Departement de Biologie, Universite Laval, G1V 0A6, Quebec, QC, Canada (2) Biology Department MS 50, Woods [...]

Movement of fishes defines the distribution and abundance of populations and occurs on a range of spatial and temporal scales. To successfully parameterise assessments and design management strategies for exploited fish populations, knowledge and consideration of their movement patterns are essential. Since the efficacy of management approaches vary depending on the sedentary or mobile nature of the target species, presence, space use and depth utilization were examined to understand the movement patterns of redthroat emperor Lethrinus miniatus. Sixty individuals were monitored for up to 12 months in an acoustic array comprising three coral reefs, and variation in space use and movement patterns was observed among 26 individuals. Half of the individuals were recorded only in proximity of one receiver along the reef edge, while the other half were detected at multiple receivers and used horizontal areas of approximately 4 [km.sup.2]. Periods of non-detection and lower detection frequency at night ([[chi square].sub.1] = 342.157, P < 0.001) indicated individuals may move away from the monitored reef edge to the adjacent sandy habitat, but most movements outside the array remain unknown. Long-distance movement was recorded for one individual, recaptured ~160 km from the release location. Generally, no trends in depth use were apparent, L. miniatus inhabited a variety of depths, which were not related to individual size or time of day, yet some effect of month was evident. Variation in movement among adult L. miniatus indicates that while some individuals undergo broaderscale movement, spatial closures that cover individual reefs (>4 [km.sup.2]) could provide protection from fishing for the proportion of the population that displayed high site fidelity and moderate-sized activity spaces (over a period of up to 12 months)., Introduction Movement defines the distribution of species in time and space, and knowledge of movement patterns is useful for understanding population dynamics and potential effects of exploitation (Pittman and McAlpine [...]

The dispersal during the planktonic larval period is a key feature to understand the metapopulation structure of marine fishes, and is commonly described by four general models: (1) lack of population structure due to extensive larval dispersal; (2) isolation by geographic distance, where larval connectivity decreases with increasing distance between sites in all directions (isotropy); (3) population structure without any clear geographic trend (chaotic); and (4) population structure explained by seascape approaches that explicitly incorporate the spatial and temporal variations in the direction and strength of oceanic currents via oceanographic modeling. We tested the four models in the Pacific red snapper Lutjanus peru, a key commercial species in the Gulf of California (GC), Mexico. We genotyped 15 microsatellite loci in 225 samples collected during 2015-2016 from 8 sites, and contrasted the observed empirical genetic patterns against predictions from each model. We found low but significant levels of population structure among sites. Only the seascape approach was able to significantly explain levels of genetic structure and diversity, but exclusively within spring and summer, suggesting that this period represents the spawning season for L. peru. We showed that in the GC, the strong asymmetry in the oceanic currents causes larval connectivity to show different values when measured in distinct directions (anisotropy). Management tools, including marine reserves, could be more effective if placed upstream of the predominant flow. Managers should consider that oceanographic distances describing the direction and intensity of currents during the spawning period are significant predictors of larval connectivity between sites, as opposed to geographic distances., Author(s): Adrian Munguia-Vega [sup.1] [sup.2] , S. Guido Marinone [sup.3] , David A. Paz-Garcia [sup.4] [sup.5] , Alfredo Giron-Nava [sup.6] , Tomas Plomozo-Lugo [sup.7] , Ollin Gonzalez-Cuellar [sup.7] , Amy [...]