Alberto F. Amorim

Trends in the exploitation of South Atlantic shark populations

Approximately 25% of globally reported shark catches occur in Atlantic pelagic longline fisheries. Strong declines in shark populations have been detected in the North Atlantic, whereas in the South Atlantic the situation is less clear, although fishing effort has been increasing in this region since the late 1970s. We synthesized information on shark catch rates (based on 871,177 sharks caught on 86,492 longline sets) for the major species caught by multiple fleets in the South Atlantic between 1979 and 2011. We complied records from fishing logbooks of fishing companies, fishers, and onboard observers that were supplied to Brazilian institutions. By using exploratory data analysis and literature sources, we identified 3 phases of exploitation in these data (Supporting Information). From 1979 to 1997 (phase A), 5 fleets (40 vessels) fished mainly for tunas. From 1998 to 2008 (phase B), 20 fleets (100 vessels) fished for tunas, swordfishes, and sharks. From 2008 to 2011 (phase C), 3 fleets (30 vessels) fished for multiple species, but restrictive measures were implemented. We used generalized linear models to standardize catch rates and identify trends in each of these phases. Shark catch rates increased from 1979 to 1997, when fishing effort was low, decreased from 1998 to 2008, when fishing effort increased substantially, and remained stable or increased from 2008 to 2011, when fishing effort was again low. Our results indicate that most shark populations affected by longlines in the South Atlantic are currently depleted, but these populations may recover if fishing effort is reduced accordingly. In this context, it is problematic that comprehensive data collection, monitoring, and management of these fisheries ceased after 2012. Concurrently with the fact that Brazil is newly identified by FAO among the largest (and in fastest expansion) shark sub-products consumer market worldwide.

Description of a Juvenile Megamouth Shark, Megachasma pelagios, Caught off Brazil

A juvenile male megamouth shark was caught by a commercial longline vessel off Brazil. This specimen is the only juvenile megamouth examined and the only one from the Atlantic Ocean. Megamouth shark is one of the rarest sharks in the world. Only 14 specimens have been reported since its description in 1983 by Taylor et al. All previous specimens examined have been adults from the Pacific and Indian Oceans. It appears that the species is cosmopolitan.

Spatio-temporal distribution and target species in a longline fishery off the southeastern coast of Brazil

In the present study, a cluster analysis, in relation to the species composition of the catches, was used to classify 6,486 fishing sets by a longline fleet based in Sao Paulo State, Brazil, from 1998 to 2006. Based on the proportions of 12 species and three broader species groups, three clusters were identified: C1: other fishes; C2: blue shark; C3: swordfish. Results indicated that the fleet targeted mainly blue shark and swordfish and also showed that the blue shark importance in this fishery has been growing progressively trough the years. Offshore areas were exploited mainly in the first and fourth quarters (from 2001 mainly), while the fishing effort was more concentrated near the continental shelf break, during the second and third quarters (for the whole period). The longline fishery based in Sao Paulo State changed fishing strategy to target different species which produced important changes in catch-per-unit-effort (CPUE) of the main species caught. Cluster analysis seems to have appropriately identified these changes over time, which is an important information, often missing in logbooks.

Reproductive biology of the spotback skate, Atlantoraja castelnaui (Ribeiro, 1907) (Chondrichthyes, Rajidae), in southeastern Brazilian waters

Especimenes de Atlantoraja castelnaui fueron obtenidos a traves de siete barcos de pesca comercial operando en aguas del sudeste brasilero, desde marzo de 2005 hasta abril de 2006. Un total de 53 machos fueron capturados y analizados, con longitudes totales comprendidas entre 17,9 y 111,0 cm. De acuerdo con el analisis de la longitud del clasper y de la glandula del clasper, peso de los testiculos, diametro de los lobulos testiculares y espinas alares, el tamano de primera madurez sexual fue estimado en 91,0 cm. Cincuenta y cuatro hembras de entre 17,4 y 116,0 cm de longitud total fueron capturadas. De acuerdo con las observaciones del ancho del utero y de la glandula oviductal, del peso de los ovarios y del diametro del mayor foliculo vitelogenico, el tamano de primera madurez sexual fue estimado en 105,0 cm. La vitelogenesis comenzaria cuando los foliculos alcanzan un tamano de 1,0 cm y la ovulacion cuando alcanzan 3,0 cm de diametro. El numero maximo de foliculos vitelogenicos observado en esta especie fue de 20. A pesar de ser A. castelnaui una especie ovipara y por tanto, con una fecundidad relativamente alta en comparacion con otros elasmobranquios, su gran tamano la convierte en una especie sumamente susceptible a la presion de pesca, siendo incluso ya considerada como especie en peligro de extincion. Por tales motivos, el conocimiento de sus parametros reproductivos podra resultar en un manejo adecuado de los stocks.

Description of diet of pelagic fish in the southwestern Atlantic, Brazil

This study reveals the food composition of pelagic fishes living in the southwestern Atlantic Ocean. As such more common pelagic species are considered to be top predators, the study proposes to know what constitutes their main food. Fish are not commonly found within their stomach contents, but instead, cephalopods are their most common food. As can be observed, Teuthida cephalopods compose their principal diet. The stomach contents of specimens of Xiphias gladius, Thunnus albacares, T. obesus, T. alalunga, Isurus oxyrinchus and Alopias superciliosus caught during July 2007 to June 2009 by using tuna longliners were studied. Teuthida cephalopods constitute the main food item for the three tuna species, while X. gladius feeds mainly on Ommastrephidae cephalopods. Though the differences among the kinds of cephalopods exist, they constitute the principal resource these fish use to live at least in the southern Atlantic Ocean.

Description of the egg capsule of Atlantoraja castelnaui (Elasmobranchii, Rajidae)

Instituto de Pesca (Av. Bartolomeu de Gusmao, 192, Ponta da Praia, 11030-906 Santos, SP, Brasil) *cristina_oddone@yahoo.com Skates (Rajidae) are oviparous and lay their eggs on the sea floor. Their large horny capsules are synthesized and secreted by the nidamental gland (WOURMS, 1977; WOURMS et al

Ecological role and historical trends of large pelagic predators in a subtropical marine ecosystem of the South Atlantic

Large pelagic predators occupy high positions in food webs and could control lower trophic level species by direct and indirect ecological interactions. In this study we aimed to test the hypotheses: (1) pelagic predators are keystone species, and their removals could trigger impacts on the food chain; (2) higher landings of pelagic predators could trigger fishing impacts with time leading to a drop in the mean trophic level of catches; and (3) recovery in the pelagic predators populations, especially for sharks, could be achieved with fishing effort reduction. We performed a food web approach using an Ecopath with Ecosim model to represent the Southeastern and Southern Brazil, a subtropical marine ecosystem, in 2001. We then calibrated the baseline model using catch and fishing effort time series from 2001 to 2012. Afterwards, we simulated the impact of fishing effort changes on species and assessed the ecological impacts on the pelagic community from 2012 to 2025. Results showed that the model was well fitted to landing data for the majority of groups. The pelagic predators species were classified as keystone species impacting mainly on pelagic community. The ecosystem was resilient and fisheries seem sustainable at that time. However, the temporal simulation, from 2001 to 2012, revealed declines in the biomass of three sharks, tuna and billfish groups. It was possible observe declines in the mean trophic level of the catch and in the mean total length of landings. Longline fisheries particularly affected the sharks, billfish and swordfish, while hammerhead sharks were mostly impacted by gillnet fishery. Model simulations showed that large sharks’ biomasses could be recovered or maintained only after strong fishing effort reduction.

Ecomorphology of oral papillae and denticles of Zapteryx brevirostris (Chondrichthyes, Rhinobatidae)

Elasmobranchs have an impressive range of highly specialized sensory systems shaped over 400 million years of evolution. The morphological analysis of oral papillae and denticle in elasmobranchs elucidates the biological role that these structures play during feeding and ventilation, bringing important descriptive information about ecological implications in an evolutionary context. The present study provides descriptions of the distribution patterns, histological characteristics and three-dimensional aspects of oral papillae and denticles in the lesser guitarfish Zapteryx brevirostris, through light microscopy and scanning electron microscopy. The presence of oral denticles in the oropharyngeal cavity suggests that this structure may have the following functions: protect against abrasion and parasites, increase the ability to grasp and hold prey and assist in reduction in hydrodynamic drag. The denticles in Z. brevirostris are similar to those found in pelagic sharks with forced ventilation (RAM). The structural conformity of denticles observed in the gill slits may facilitate water flow during prey grasp and food processing. This study supports the hypothesis that these structures may be an adaptive reflection shaped by feeding habits, capture strategies and processing prey.

A DNA tool for the identification of heavily exploited Atlantic billfishes

Due to the morphological similarities among species, the International Commission for the Conservation of the Atlantic Tunas has recommended the use of diagnostic molecular tools to allow for robust species-level identifications of the billfishes. In this study, a protocol for the molecular identification of all six Atlantic billfishes was developed utilizing a PCR–RFLP approach, targeting the mitochondrial gene cytochrome c oxidase subunit 1. A survey of 28 restriction endonucleases identified two enzymes (TaqI and HaeIII) that produced species-specific banding patterns sufficient to distinguish species. The protocol was validated against billfishes captured across their Atlantic distributions.

Morphological observations of ampullae of lorenzini in Squatina guggenheim and S. occulta (Chondrichthyes, Elasmobranchii, Squatinidae).

We have conducted a morphological study of the ampullae of Lorenzini on two shark species from Squatina Genus. In both species, S. guggenheim and S. occulta, the ampullae were observed like small pores scattered in the head region similar to other species of the Chondrichthyes Class. However, differently of the other species a greatest density of ampullae of Lorenzini was observed along of the body surface. After fixation using 10% formaldehyde, the ampullae were removed and processed for light and scanning electron microscopy. Macroscopically, the two shark species differed by the presence of dorsal spines that appeared from the head to the first dorsal fin in S. guggenheim and were absent in S. occulta. Microscopically, there were no differences between the ampullae of Lorenzini channels in these two species. The wall of the ampulla was formed by a simple squamous epithelium. Bands of connective tissue, hyaline cartilage and collagen fibers were found between the ampulla and the skeletal striated muscle layer. Nerve branches responsible for conducting signal pulses to the central nervous system were visible between the muscle and connective tissue layers. Using scanning electron microscopy and histological analysis, we found that the channels were twisted and positioned parallel to the skin. The inside of the channels contained a large amount of a gelatinous secretion composed by polysaccharides. Therefore, we conclude that the morphological combination of extended distribution of the ampullae of Lorenzini and the body shape may represent an adaptation of these species to their way of life. Microsc. Res. Tech. 75:1213–1217, 2012.