Broadnose sevengill sharks Notorynchus cepedianus caught in a recreational fishery during a 3 yr period in Anegada Bay, Argentina were examined. Monthly variations in abundance were found, with the highest mean abundance in April. Neonates and juveniles were common in the study area, indicating that Anegada Bay is a nursery area of N. cepedianus. Male and female sizes at maturity were 170 and 224 cm total length (TL), respectively, similar to other studied regions. Liver size was sexually dimorphic, with adult females having larger livers, which might allow for the maximization of oocyte size/number. Individuals <100 cm TL fed mainly on teleosts, sharks 100 to 170 cm TL consumed mainly cartilaginous fishes and less teleosts, and sharks >170 cm fed mostly on cartilaginous fishes and marine mammals. All size groups preyed on marine mammals, which may be a result of the local availability of small calves of La Plata River dolphins Pontoporia blainvillei. Possibly, the pattern of habitat use of Anegada Bay by P. blainvillei is affected by N. cepedianus. The proportion of individuals with prey within the stomach was negatively correlated with TL. As indicated by prey remains found within stomachs (most were in pieces) and by the location of the fishing hook in sharks (most were hooked in the mouth), N. cepedianus extensively handles its prey with the mouth before swallowing it, which is consistent with previous observations. Anegada Bay may be an important area for conservation of N. cepedianus in the SW Atlantic given the high abundance of juveniles and subadults. KEY WORDS: Elasmobranch · Maturity · Nursery · Predation · Marine mammalsResale or republication not permitted without written consent of the publisher

This study analyses the sexual activity and segregation of sand tiger sharks, Carcharias taurus, from Anegada Bay (Argentina). Reproduction-linked movements along the South American Atlantic coast were inferred from data from several SW Atlantic localities. Male sand tigers (n=162) matured at 193 cm total length (L T). Females (n=77) matured between 218 and 235 cm L T. These figures are similar to those from other populations, although size-at-maturity of males was slightly different from South African and Australian populations. In females, the size of ovarian follicles was positively correlated with gonadosomatic index and negatively correlated with hepatosomatic index, while the liver was significantly larger than in males. Sand tiger sharks were present in Anegada Bay from December to April. Males were significantly more abundant than females (2:1). Significant differences in reproductive condition through time were observed in males. During January and February males had seminal vesicles full of spermatozeugmata but by March and April the vesicles were empty. As the proportion of males with a lighter colouration peaked from January to March, it is very likely that mating takes place during January and February. The skewed sex-ratio during the mating season indicates a possible strong competition for mates among males, as observed in captivity. Males, females and some juveniles occur in Argentinean and Uruguayan waters, where mating takes place. Pregnant females occur in subtropical waters of southern Brazil, where they give birth. Given that pregnant and non-pregnant females occur at the same time in different zones, we suggest that the female reproductive cycle is biennial. Striking differences among migratory patterns of sand tiger sharks from the SW and NW Atlantic and South Africa were observed.

Ontogenetic diet shifts are a widespread phenomenon among vertebrates, although their relationships with life history traits are poorly known. We analyzed the relative importance of body size, age and maturity stage as determinants of the diet of a marine top predator, the copper shark, Carcharhinus brachyurus, by examining stomach contents using a multiplehypothesis modeling approach. Copper sharks shifted their diet as size and age increased and as they became sexually mature, incorporated larger prey as they grew, and had a discrete shift in diet with body size, with only individuals larger than %200 cm total length able to prey on chondrichthyans. Body size was the most important trait explaining the consumption of chondrichthyans, while age determined the consumption of pelagic teleosts. Pelagic teleosts were consumed mostly by mediumaged sharks, a result, probably, of a risk-reducing feeding strategy at young ages coupled with either a senescence-related decline in performance or a change in sensory capabilities as sharks age. Copper sharks of all sizes were able to cut prey in pieces, implying that gape limitation (i.e., the impossibility of eating prey larger than a predator's mouth) did not play a role in producing the diet shift. Our results suggest that, contrary to the current practice of setting minimum but not maximum size limits in catches, any plan to conserve or restore the ecological function of sharks, through their predatory control of large prey, should aim to maintain the largest individuals.

The foraging ecology of the school shark Galeorhinus galeus was studied in Anegada Bay, Argentina, during the seasonal occurrence of this species in Argentinean waters (October to April) from 1998 to 2001. Of the 408 individuals examined, 168 (41.2%) had food remains in their stomachs. The proportion of individuals with food remains was negatively correlated with total length. In general, the diet was composed mainly of teleosts (98.5% IRI [index of relative importance]

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The histology of the pharyngeal cavity and oesophagus of the freshwater 'silverside'Odontesthes bonariensis (Cuvier and Valenciennes) and the characteristics of their mucous cells were investigated. The histological characterization of its digestive wall revealed that the mucosa is thrown with longitudinal folds. The epithelium covering the folds was stratified with abundant mucous cells and gustative corpuscles, which are lacking in the oesophagus. The muscularis mucosa was absent. The submucosa presented the compactum stratum. The muscularis was organized in longitudinal and circular layers of muscular striated fibres. The serosa with a flat epithelium was located only in the oesophagus. Using histochemical procedures including methods for localization and characterization of glycoproteins (GPs), no differences were detected between the mucous cells contents of the pharyngeal cavity and those of the oesophagus. The mucous cells showed a weak periodic acid-Schiff (PAS) positive reaction in their content. The reactions for the differential analysis of sialic acids from GPs are feeble for periodic acid-Schiff at low temperature and low pH (PA*S) and KOH/PA*S and strong for periodic acid/borohydride/KOH/PAS (PA/Bh/KOH/PAS) and KOH/PA*/Bh/PAS revealing the scarce presence of C7 or C9 substituted and non-substituted sialic acids and the abundance of C7, C8 substituted sialic acids, O-acyl sugars and neutral sugars respectively. The results suggest that the pharyngeal cavity with the gustative corpuscles would induce the gastric secretion whereas the oesophagus is mainly involved in the transport of the food bolus to the stomach with the aid of abundant secretion of mucus. GPs secreted on the surface of the mucous cells, likely related to environmental conditions, would be involved in the lubrication, protection against abrasion and inhibition of microorganism proliferation.

The feeding habits of the sand tiger shark Carcharias taurus, one of the most threatened sharks of the world, are poorly known. Sand tiger sharks are critically endangered in the South-west Atlantic. Since 2007, the law requires that all individuals caught in recreational fisheries off Argentina must be released. Using data from a north Patagonian recreational fishery (n = 164 stomachs with contents), we analyzed the diet of sand tiger sharks in relation with size, sex, maturity stage and season; assessed prey consumption patterns and hooking location; and estimated diet overlap with fishery landings. Sand tiger sharks consumed mainly teleosts (55.4% of the total prey number, N) and elasmobranchs (41.84% N), and ate more benthic elasmobranchs (batoids and angel sharks) as they become larger. Sharks swallowed prey mostly in one piece (93.7%) and were hooked mainly in internal organs (87.4%, n = 175), causing occlusion and perforation of the esophagus and stomach, and lacerations to the pericardium, heart and liver. Sand tiger sharks fed on the most heavily landed species, overlapping almost completely (490%) with fishery landings. Conservation plans should take into account that releasing hooked sharks could be insufficient to minimize fishing mortality and that competition for food with fisheries is likely to occur.