Agnaldo Silva Martins

Diet and feeding of the cutlassfish Trichiurus lepturus in the Subtropical Convergence Ecosystem of southern Brazil

The diet and feeding of the cutlass¢sh Trichiurus lepturus were studied based on analyses of the stomach contents of larvae, juveniles, and adults collected along the continental shelf and shelf break oi southern Brazil, from the Cape of Santa Marta Grande (28836 0 S) to Chu|¤ (34845 0 S). The larvae and pre-juveniles with a total length of 55 cm were found to have fed almost exclusively on calanoid copepods, whereas juveniles (5 to 30 cm) fed on small zooplanktonic crustaceans such as Lucifer faxoni and Promysys atlantica. On the other hand, sub-adults (30 to 70 cm), fed on euphausiids, mainly Euphausia similis, and small ¢sh, mostly anchovy Engraulis anchoita. Adults (70 to 160 cm) fed on a wide range of larger prey, such as anchovy, sciaenid ¢sh, cephalopods and coastal shrimps, as well as euphausiids. The juveniles and sub-adults fed more intensively than adults during the warm-water season whereas adults fed more intensively during the cold-water season. Feeding activity was more intense at night, while cannibalism was more frequent during the warm season, when biological productivity was lower. Finally, diet diversity was higher in coastal waters, during the warm season. The abundance of cutlass¢sh oi southern Brazil may be explained by the fact that it is adapted to feed on a wide size-range of both pelagic and demersal prey.

Debris ingestion by juvenile marine turtles: An underestimated problem

Marine turtles are an iconic group of endangered animals threatened by debris ingestion. However, key aspects related to debris ingestion are still poorly known, including its effects on mortality and the original use of the ingested debris. Therefore, we analysed the impact of debris ingestion in 265 green turtles (Chelonia mydas) over a large geographical area and different habitats along the Brazilian coast. We determined the death rate due to debris ingestion and quantified the amount of debris that is sufficient to cause the death of juvenile green turtles. Additionally, we investigated the original use of the ingested debris. We found that a surprisingly small amount of debris was sufficient to block the digestive tract and cause death. We suggested that debris ingestion has a high death potential that may be masked by other causes of death. An expressive part of the ingested debris come from disposable and short-lived products.

Distribution, abundance and biological interactions of the cutlassfish Trichiurus lepturus in the southern Brazil subtropical convergence ecosystem

Abstract The distribution, abundance and biological interactions of the cutlassfish Trichiurus lepturus in the southern Brazil subtropical convergence ecosystem were studied from demersal trawl surveys conducted along the continental shelf and upper slope from Cape Santa Marta Grande (28 °36′S) to Chui (34 °45′S) between 1981 and 1987. Trichiurus lepturus was more abundant at bottom water temperatures of over 16 °C and in the 40–120 m depth range. From late spring to fall, juveniles of 5–30 cm total length ( TL ) were found in coastal waters, subadults ( TL 30–70 cm) mainly in inner shelf waters and adults ( TL > 70 cm) in coastal, inner and outer shelf waters. Higher catches of subadults and adults were found associated with thermal fronts in the western boundary of the Subtropical Convergence or with a shelf break upwelling observed in summer. The standing stock in a 58 000 km 2 shelf area estimated by the swept area method, ranged from 3066 t (±46% CI ) in September 1981 to 37814 t (±22% CI ) in January 1982. Correlation between occurrences of different size groups of cutlassfishes and other fishes caught in 250 bottom trawl hauls was analyzed. A positive correlation between cutlassfish and juvenile weakfish, Cynoscion guatucupa , was associated with similar spatial distribution but also indicated trophic competition.

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.

Relationship between fibropapillomatosis and environmental quality: a case study with Chelonia mydas off Brazil

We documented the presence of fibropapillomatosis (FP), a debilitating tumor-forming disease, in marine turtles in Espirito Santo Bay (Brazil) from March 2007 to April 2008, and assessed the value of a specific environmental index for predicting the prevalence of FP. Turtles were captured monthly with entanglement nets and scored for presence and severity of FP. For the assessment of habitat quality, we used the ecological evaluation index (EEI) based on benthic macrophytes. The FP-free control area was classified as good quality (EEI = 8) and the study area, with high FP prevalence, was classified as bad quality (EEI= 2). Prevalence of FP in the study area was 58.3% with an average of 40 tumors per individual, and prevalence varied positively with curved carapace length (CCL). No FP was seen in the control area. The number of turtles heavily afflicted (tumor score category 3) was 10 times larger than those lightly affected (tumor score category 1). Most tumors were found on or near the front and rear flippers; no oral tumors or internal tumors were found. At recapture, 41% of formerly tumor-free turtles revealed FP, often increasing in severity with time, and very few turtles showed signs of disease regression. From the results of this study we concluded that FP is particularly severe in Espírito Santo Bay. Future studies should focus on evaluating how widespread FP is in Brazil, whether prevalence is increasing or decreasing, and elucidating the pathology and pathogenesis of FP in sea turtles in Brazil.

Coastal habitat degradation and green sea turtle diets in Southeastern Brazil.

To show the influence of coastal habitat degradation on the availability of food for green turtles (Chelonia mydas), we assessed the dietary preferences and macroalgae community at a feeding area in a highly urbanized region. The area showed low species richness and was classified as degraded. We examined stomach contents of 15 dead stranded turtles (CCL=44.0cm (SD 6.7cm)). The diet was composed primarily of green algae Ulva spp. (83.6%). In contrast, the macroalgae community was dominated by the green alga Caulerpa mexicana. We found a selection for red algae, seagrass and Ulva spp., and avoidance for C. mexicana and brown alga Dictyopteris delicatula. The low diversity of available food items, possibly a result of environmental degradation, likely contributed to the low dietary diversity. The nutritional implications of this restricted diet are unclear.

Age and growth of coney (Cephalopholis fulva), from the central coast of Brazil

Coney (Cephalopholis fulva) otoliths were collected from 1997 to 1999 off the central coast of Brazil. Analysis of the edges of otoliths sections suggests that one translucent and one opaque zone are formed once a year. Coney age and size-ranges were 2-25 years and 172-428 mm total length (TL) respectively. The von Bertalanffy growth equation was TL t =316(1-e -0.138(t+5.301) ). The maximum age observed in this study is well above that previously reported for coney.

Impact of commercial fishing on Trindade Island and Martin Vaz Archipelago, Brazil: characteristics, conservation status of the species involved and prospects for preservation

Visual records, radio interviews and onboard observ ations of the fishing activities during a 58 days s cientific expedition to Trindade Island and the Martin Vaz Ar chipelago were obtained from February to April 2007 . The regular activities of four different fisheries were observed: pelagic longline, bottom line, trolling and handline. These fisheries caused mortality of at least seven species with some level threat, according to the In ternational Union for Conservation of Nature list. The establis hment of specific restriction norms for hook-and-li ne activities around the oceanic islands was seen as an alternati ve for the conservation of the ichthyofauna of the region. Satellite monitoring to track the fishery vessels c ould be established through the national program as another legal mean to diminish fishing the impact.

The anti-predator role of within-nest emergence synchrony in sea turtle hatchlings

Group formation is a common behaviour among prey species. In egg-laying animals, despite the various factors that promote intra-clutch variation leading to asynchronous hatching and emergence from nests, synchronous hatching and emergence occurs in many taxa. This synchrony may be adaptive by reducing predation risk, but few data are available in any natural system, even for iconic examples of the anti-predator function of group formation. Here, we show for the first time that increased group size (number of hatchlings emerging together from a nest) reduces green turtle (Chelonia mydas) hatchling predation. This effect was only observed earlier in the night when predation pressure was greatest, indicated by the greatest predator abundance and a small proportion of predators preoccupied with consuming captured prey. Further analysis revealed that the effect of time of day was due to the number of hatchlings already killed in an evening; this, along with the apparent lack of other anti-predatory mechanisms for grouping, suggests that synchronous emergence from a nest appears to swamp predators, resulting in an attack abatement effect. Using a system with relatively pristine conditions for turtle hatchlings and their predators provides a more realistic environmental context within which intra-nest synchronous emergence has evolved.

Mesophotic fishes of the Abrolhos Shelf, the largest reef ecosystem in the South Atlantic.

Fishes inhabiting rhodolith beds and reefs at mesophotic depths on the Abrolhos Shelf, which encompasses the largest and richest coral reef formation in the South Atlantic Ocean, were assessed through technical diving and remotely operated vehicles (ROVs). A total of 74 fish species were recorded, including at least one new species, one new record for the south-western Atlantic and six new records for the Abrolhos region. Overfishing, mining and port activities are already threatening many endangered and commercially important species recorded on the mesophotic reefs of Abrolhos Shelf, and the establishment of marine protected areas and off-reserve fisheries regulations are urgently needed.