Néstor F. Ciocco

Volutid Snails as an Alternative Resource for Artisanal Fisheries in Northern Patagonic Gulfs: Availability and First Suggestions for Diving Catches

Abstract Volutid snails have been identified as a potential resource for artisanal fisheries in northern patagonic gulfs. We explored their availability in two gulfs of Chubut Province (Patagonia, Argentina) by means of SCUBA diving and baited traps. CPUE and biomass were estimated from visual counting densities. CPUE of all the volutes was 65.85 kg·diver−1·h−1 and 59.5 kg·diver−1·h−1 in San Matías (SMG) and San Jorge (SJG) Gulfs, respectively. Estimated biomass was 89.7 (±28.9) and 44.4 (±19.2) tons in SMG and SJG. The species Adelomelon ancilla and Odontocymbiola magellanica could supplement the potential clam fishery existent at SJG. In SMG Zidona followed by O. magellanica could be the main commercial target. We suggest minimum catch sizes of 16 cm for Z. dufresnei, 9 cm for O. magellanica, and 12 cm for A. ancilla. Protection of the egg capsules and females would help the protection of the resource. These measures could ensure the sustainability of a small-scale multispecific fishery.

Differences in individual growth rate among scallop (Chlamys tehuelcha (d'Orb.)) populations from San José Gulf (Argentina)

Abstract Differences in mean individual growth rate between populations of Chlamys tehuelcha (dOrb.) from San Jose Gulf (Argentina) have been reported. These differences may reflect an environmental gradient in food availability. The objectives of this study were (a) to document statistically differences in scallop growth between several grounds of San Jose Gulf and (b) to discuss the consistency of the pattern with two alternative hypotheses: (H1) a gradient in food availability and (H2) density dependence. Two types of data were used to estimate growth rate: growth rings (five grounds) and the monthly average size (during 3 years) of closely monitored strong cohorts (three grounds). The biomass and density of all scallop year classes, temperature and chlorophyll a were recorded monthly in the three grounds monitored. Carrying capacity (calculated annual production of bivalve meat, given net annual phytoplankton production) and annual production of scallop meat were estimated in the three grounds where cohorts were monitored. Statistically significant differences in individual growth rate were detected between populations. Growth was greater in the N and SW, and less in the SE of the Gulf. Environmental data were consistent with the food availability hypothesis. Growth rate was not correlated with mean scallop biomass (annual or 3 year averages). Estimated carrying capacity was lower in the SE than in the SW and N of the Gulf. Measured annual production of scallop meat and calculated carrying capacity were similar at each locality, independent of biomass. Intrapopulational variation in growth due to density dependence is very small compared to interpopulational differences due to food availability.

Chapter 26 Argentina

Publisher Summary This chapter discusses the two species, Aequipecten tehuelchus (Tehuelche scallop) and Zygochlamys patagonica (Patagonic scallop), their fisheries, and experimental results that have significance in the future development of aquaculture. The fisheries supported by these two species are radically different from each other. The Tehuelche scallop is the target of small inshore fisheries in the gulfs of northern Patagonia, and involves dredging and commercial diving. In spite of the small volumes landed, these fisheries are of considerable significance for the local economies. The Patagonic scallop fishery is an industrial operation conducted by three or four factory trawlers that process the catch at sea. Catches in the order of 50,000 tons yr -1 now rank this species among the most important scallop fisheries in the World. The Tehuelche scallop is a simultaneous hermaphrodite and is iteroparous. The Tehuelche scallop may do quick and brief swimming movements as an escape response to the predators or other disturbances.

Reproductive cycle of the southern geoduck clam, Panopea abbreviata (Bivalvia: Hiatellidae), in north Patagonia, Argentina

Summary On the basis of histological examination, we present the first description of gametogenesis in Panopea abbreviata. Six stages of gonad development were identified using morphological and histochemical criteria. The gonads are diffuse and cannot be sexed with the naked eye. The analyses of gonad tissues showed that the gametogenic cycle is continuous with no resting period. Ripe individuals of both sexes were found for most of the year, and the spawning season seems to be protracted. The application of histological techniques to individuals collected monthly revealed a bias in the sex ratio depending on the body length. Even when the sex ratio was balanced in large clams, for small individuals, the sex ratio was biased in favour of the males. Although no hermaphroditic individuals were found in our samples, the possibility of protandry should be examined further.

Implications of biological factors on accumulation of persistent organic pollutants in Antarctic notothenioid fish

In the present study, the possible associations between selected persistent organic pollutants (POPs) and biological factors were assessed in different tissues of two Antarctic notothenioid fish: Notothenia rossii (NOR) and Trematomus newnesi (TRN) collected at Potter Cove, King George Island/Isla 25 de Mayo, South Shetland Islands. Specifically, association patterns between biological factors (body size, lipid content, body condition) and POP concentrations (polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT) and metabolites, polybrominated diphenyl ethers (PBDEs), and hexachlorocyclohexane (HCH), hexachlorobenzene (HCB), chlordanes (CHLs) and methoxylated polybrominated diphenyl ethers (MeO-PBDEs)), were explored by using two approaches: multivariate analyses (principal component analysis: PCA) and intraspecific correlations. Integrating results suggest that biological factors such as size, KI and tissue type seemed to be associated to selective accumulation of POPs for immature specimens of N. rossii, and KI and tissue type for mature specimens of T. newnesi. Each particular factor should be considered when choosing N. rossii or T. newnesi as sentinels for POPs pollution in Antarctic marine environments. Further, both nototheniids showed a selective accumulation pattern in their gonads of penta-chlorinated biphenyls (penta-CBs; 55.5 and 29ngg-1 lw for N. rossii and T. newnesi, respectively) and organochlorine pesticides such as DDTs (199 and 13.3ngg-1 lw, for N. rossii and T. newnesi respectively), and of polybrominated diphenyl ethers (PBDEs) in gills (97.2 and 22.1 for ngg-1 lw, for N. rossii and T. newnesi, respectively), highlighting the importance of these tissues in monitoring studies of pollution in fish. The current study expands the knowledge concerning the biological factors to be investigated when specific pollutants are monitored and supports the importance of tissue type for the selective accumulation of POPs in Antarctic fish. Additionally, a contribution to the scarce data on concentration of MeO-PBDEs in Antarctic marine organisms, particularly in the highly diverse perciform suborder Notothenioidei is provided.