Jean-Christophe Joyeux

Fish Biodiversity of the Vitória-Trindade Seamount Chain, Southwestern Atlantic: An Updated Database

Despite a strong increase in research on seamounts and oceanic islands ecology and biogeography, many basic aspects of their biodiversity are still unknown. In the southwestern Atlantic, the Vitória-Trindade Seamount Chain (VTC) extends ca. 1,200 km offshore the Brazilian continental shelf, from the Vitória seamount to the oceanic islands of Trindade and Martin Vaz. For a long time, most of the biological information available regarded its islands. Our study presents and analyzes an extensive database on the VTC fish biodiversity, built on data compiled from literature and recent scientific expeditions that assessed both shallow to mesophotic environments. A total of 273 species were recorded, 211 of which occur on seamounts and 173 at the islands. New records for seamounts or islands include 191 reef fish species and 64 depth range extensions. The structure of fish assemblages was similar between islands and seamounts, not differing in species geographic distribution, trophic composition, or spawning strategies. Main differences were related to endemism, higher at the islands, and to the number of endangered species, higher at the seamounts. Since unregulated fishing activities are common in the region, and mining activities are expected to drastically increase in the near future (carbonates on seamount summits and metals on slopes), this unique biodiversity needs urgent attention and management.

Trace metal contamination in estuarine fishes from Vitória Bay, ES, Brazil

Muscular tissue from wild-caught mullet (Mugil spp.) and snook (Centropomus spp.) was analyzed by atomic absorption spectrometry to determine muscle contamination levels for cadmium, chromium, copper, lead and zinc and evaluate risks to human health associated with seafood consumption. Fishes were captured by subsistence fishermen in Vitoria Bay, a Brazilian tropical estuary with numerous outfalls of untreated industrial and residential sewage. Based on the premisses that subsistence fisherman and local consumer show weak (culinary or other) preferences within the taxa studied, analyses were conducted and results are reported for genera. Snook cadmium, chromium, copper and zinc concentrations were positively correlated with size or weight. Mullet chromium concentration decreased with size. Cadmium and lead were higher and zinc lower in mullet than in snook. Summer cadmium and lead concentrations were higher than in winter. Chromium presented concentrations consistently over the legal Brazilian limit for seafood. However, the greatest health concern was probably related to lead concentration, especially in respect to consumption by young children.

Constraints on Coastal Lagoon Fisheries

ABSTRACT We have estimated the individual and synergetic effects of geographical, morphometrical, environmental and anthopogenic parameters on the fishery yield of coastal lagoons throughout the world. For this analysis we have relied on published literature and other information obtained directly from researchers and fishery officials, since special global scale sampling was not possible. Lagoons that are exploited through alternative fishery practices had significantly higher yields than the others. The fishery yield was dependent upon a lagoon’s geographical location and morphometry. The significant environmental and anthropogenic factors determining the yield were the exchanges of water between lagoons and the ocean, the physico-chemical properties of the water, the extent of aquatic vegetation, and the fishing pressure. Overall, the results show the single influence of freshwater input to be negligible while the influence of oceanic tide exercised through the inlets was significant. Fishery yield appeared to be correlated with the mean annual concentration of nitrites. Submerged and emerged vegetation were good indicators for fishery productivity. The single most influential factor of all was the fishing pressure. Data collected for 292 fished lagoons are given in appendix tables and include annual fishery yield; water area; mean and maximum depth; watershed area; annual freshwater inputs; inlet(s) width; height of ocean tide; minimum and maximum temperatures and salinities; mean and maximum concentrations of nitrite, nitrate, and orthophosphate; areas of immersed and emergent vegetation; and number of fishermen.

Ambicoloration and morphological aberration in the sole Achirus declivis (Pleuronectiformes: Achiridae) and two other cases of color abnormalities in achirid soles from southeastern Brazil

Three cases of color abnormalities and one of morphological aberration in flatfishes of the genus Achirus are described from the Piraque-Acu River estuary, Espirito Santo, Brazil. One specimen of A. declivis has 75% of the blind side with coloration like that of the ocular side. Another specimen of the same species is strongly hypomelanistic. A third specimen has incomplete eye rotation and a hooked dorsal fin. An ambicolored A. lineatus is also described.

The abundance of fish larvae in estuaries: Within-tide variability at inlet and immigration

The larvae of winter spawning fishes immigrating through Beaufort Inlet into the Pamlico Sound estuarine system (North Carolina, United States) were passively sampled during 14 flood tides and nine of the following ebb tides. Five taxa were abundant in the catches. Pelagic species were represented by Atlantic menhaden, Brevoortia tyrannus. Nonpelagic taxa were represented by Atlantic croaker, Micropogonias undulatus, spot, Leiostomus xanthurus, pinfish, Lagodon rhomboides, and flatfishes of the genus Paralichthys. The sampling was continuous and the sample duration varied between 4 min and 32 min. The longest samples furnished the most accurate and precise estimates of the mean tidal abundance. Sampling 10 min each hour of the tide was the most efficient protocol for determining the mean tidal abundance. The abundance patterns was shown to differ according to the pelagic or nonpelagic behavior of the larvae. Analyses suggested the nonpelagic taxa rely on astronomical tides and vertical migrations synchronous with the direction of the tide flow to be transported upstream in the estuary. These larvae were not dependent upon the strength of the tide to penetrate the inlet. In contrast, menhaden larvae seemed to rely primarily on strong food tides to enter the estuarine area, probably because the vertical positioning of the species within the water column is not dependent upon the direction of the tide. However, if larvae were present outside of the inlet, strong flood tides indiscriminately brought pelagic and nonpelagic species into the estuary.

Diet and food partitioning between juveniles of mutton Lutjanus analis, dog Lutjanus jocu and lane Lutjanus synagris snappers (Perciformes: Lutjanidae) in a mangrove‐fringed estuarine environment

Diet of juvenile mutton Lutjanus analis, dog Lutjanus jocu and lane Lutjanus synagris snappers were studied in the tropical Brazilian estuarine system of the Piraquê-açú and Piraquê-mirim Rivers to determine how these species share the resources in this restricted space. The three species prey principally upon Peracarida (L. synagris: relative importance index I(RIc) = 29%), Natantia (L. analis and L. synagris: I(RIc) = 39 and 38%, respectively), Reptantia (L. analis and L. jocu: I(RIc) = 28 and 43%, respectively) and Teleostei (L. jocu: I(RIc) = 24%). The three species use estuaries as nursery habitats but food overlap was not biologically significant due to a combination of interspecific differences in size, spatial distribution, microhabitat preferences and seasonal patterns of abundance and prey choice. Large marine protected areas incorporating essential habitats for all life stages are suggested to be the best tool for the management of these economically important species.

Growth of Juvenile Centropomus undecimalis in a Tropical Island

Age, growth rates and hatching dates were determined for juvenile common snook, Centropomus undecimalis, collected in several Puerto Rican estuarine systems. Two growth models (von Bertalanffy and power curve) were used and compared based on the fitting, the residual distribution and homogeneity of variances. A multiple linear regression was also fit to predict age from otolith weight, fish weight and standard length. Hatching dates back-calculated from age estimates, suggested that spawning occurs throughout the year but peaks from May to October. Early juveniles (age < 100 d) recruited during the wet season (August to November) showed a significantly higher growth rate (0.67 mm d−1) than the dry season (December to July) recruits (0.41 mm d−1). These results are compared with snook collected in west Florida.

Island biogeography of marine organisms

Studies on the distribution and evolution of organisms on oceanic islands have advanced towards a dynamic perspective, where terrestrial endemicity results from island geographical aspects and geological history intertwined with sea-level fluctuations. Diversification on these islands may follow neutral models, decreasing over time as niches are filled, or disequilibrium states and progression rules, where richness and endemism rise with the age of the archipelago owing to the splitting of ancestral lineages (cladogenesis). However, marine organisms have received comparatively little scientific attention. Therefore, island and seamount evolutionary processes in the aquatic environment remain unclear. Here we analyse the evolutionary history of reef fishes that are endemic to a volcanic ridge of seamounts and islands to understand their relations to island evolution and sea-level fluctuations. We also test how this evolutionary history fits island biogeography theory. We found that most endemic species have evolved recently (Pleistocene epoch), during a period of recurrent sea-level changes and intermittent connectivity caused by repeated aerial exposure of seamounts, a finding that is consistent with an ephemeral ecological speciation process. Similar to findings for terrestrial biodiversity, our data suggest that the marine speciation rate on islands is negatively correlated with immigration rate. However, because marine species disperse better than terrestrial species, most niches are filled by immigration: speciation increases with the random accumulation of species with low dispersal ability, with few opportunities for in situ cladogenesis and adaptive radiation. Moreover, we confirm that sea-level fluctuations and seamount location play a critical role in marine evolution, mainly by intermittently providing stepping stones for island colonization.

Target fishes on artificial reefs: evidences of impacts over nearby natural environments.

Topics in artificial reef research have included a wide number of themes but a major portion of published works are about the attraction that artificial reefs exert over fishes that reside in natural reefs. In the present work, underwater visual censuses of fishes were conducted at both artificial and natural reefs, aiming at verifying whether fishes are attracted or and produced on artificial reefs. Length frequency, mean biomass and frequency of occurrence of four fish genera targeted by local fisheries (Caranx, Haemulon, Lutjanus and Mycteroperca) were compared between two artificial and two natural reefs. Evidences of both production and attraction of target reef fishes by artificial reefs were found. Production is evidenced by the enormous abundance of recruits of a single grunt species, the tomtate (Haemulon aurolineatum Cuvier). The high concentration of adults of predator demersal fishes (Mycteroperca spp. and Lutjanus spp.), present at low density on natural reefs, is the main evidence for attraction by artificial reefs. Results are inconclusive for the pelagic predators Caranx spp. The attraction that artificial reefs exert over large demersal predators can negatively affect nearby natural areas through shifts in predation, competition or nutrient input. Production can affect benthic communities in soft bottoms adjacent to artificial reefs by foraging of reef-associated fishes. Even when unplanned for fisheries purposes artificial reefs are often submitted to commercial and recreational fisheries and, due to the strong attraction they exert over large predators, these structures need harvest regulations.

Distribution and Population Structure of Callinectes danae (Decapoda: Portunidae) in a Tropical Brazilian Estuary

Abstract The portunid crab Callinectes danae is abundant in Brazilian estuaries and coastal areas and is an important item to artisanal fisheries. This study investigated the distribution and population structure by sex and size, the size at sexual maturity, and sex-ratio of the species in Vitória Bay, Espírito Santo, southeastern Brazil. Crabs were collected monthly by nocturnal trawling during one year in six sampling stations distributed along an estuarine gradient and an independent depth gradient. Physico-chemical parameters of water were measured in situ on each station. A total of 3876 individuals were collected: 2537 females (1147 adults, 318 ovigerous, and 1072 juveniles), and 1339 males (444 adults and 895 juveniles). The mean carapace width (including lateral spines) at sexual maturity was 91.3 mm for males and 80.5 mm for females; the female-to-male sex ratio was 1.89∶1. Adult females occurred throughout the bay and year-round, but egg-bearing females were almost exclusively caught in deep and high salinity areas. Adult males and juveniles of both sexes occurred mainly in internal areas of the estuary, nearest river mouths; highest captures were registered in November. Both the scarcity of males, probably resulting from size-selective catch, and the low proportion of ovigerous females, compared with that observed in other Brazilian estuaries, suggest that the population has been overexploited.