Jose Maria Orensanz

Institutions, incentives and the future of fisheries

Fisheries around the world are managed with a broad range of institutional structures. Some of these have been quite disastrous, whereas others have proven both biologically and economically successful. Unsuccessful systems have generally involved either open access, attempts at top–down control with poor ability to monitor and implement regulations, or reliance on consensus. Successful systems range from local cooperatives to strong governmental control, to various forms of property rights, but usually involve institutional systems that provide incentives to individual operators that lead to behaviour consistent with conservation.

Chapter 14 Dynamics, assessment and management of exploited natural populations

Publisher Summary This chapter discusses the dynamics, assessment, and management of exploited natural populations. All scallop stocks are structured as “metapopulations” in which subpopulations of sedentary post-larval individuals are connected with each other through the dispersal of pelagic larvae. The metapopulation is a useful conceptual framework for the analysis and management of benthic fisheries. Emphasis on spatial structure brings with it, the need to identify appropriate spatial scales for the observation, analysis and management of exploited scallop stocks. The hierarchy of spatial scales presented by Orensanz and Jamieson is adopted in the chapter. The primary factors tuning year-class-strength are those that affect advection and survival of pelagic larvae. These factors pertain largely to oceanographic conditions. It is natural that research on modulation of year-class-strength and the search for signs of climatic forcing focus on abundance indices aggregated at relatively large spatial scales. The empirical evidence about the influence of climate on larval availability and recruitment is considered. The transition between the two stages—namely, pelagic larvae and recruits is modulated by factors other than larval availability. The elusive relationship between aggregate spawning stock and recruitment is also discussed.

Distinctness, phylogenetic relations and biogeography of intertidal mussels ( Brachidontes , Mytilidae) from the south-western Atlantic

Rocky shore intertidal communities along the cold- and warm-temperate coasts of the south-western Atlantic are dominated by small mussels of the genus Brachidontes s.l . (Mytilidae), yet the status of species occurring in the region remains unresolved. Taxonomic studies have been based on shell morphology, but high phenotypic variability has led to much confusion. Based on mitochondrial and nuclear genes (COI, 28S rDNA and ITS1) from nine localities in Uruguay and Argentina we confirmed the occurrence of three species in the south-western Atlantic: Brachidontes darwinianus and B. rodriguezii in the warm-temperate and B. purpuratus in the cold-temperate sector. The latter two species coexist in the same beds along the transition zone (41–43°S). The phylogeny based on mitochondrial and nuclear genes, indicate an early divergence of B. purpuratus . At the intra-specific level, low genetic differentiation and absence of fossil record for B. purpuratus from the earlier Quaternary marine terraces of Patagonia likely result from a relatively recent (post-LGM) colonization originated from populations in the south-eastern Pacific. In the case of B. rodriguezii , by contrast, genetic intraspecific differentiation, a fossil record of phenotypically-related forms going back to the Late Miocene, and phylogenetic position in the COI-based phylogeny, prompts the hypothesis that this species is derived from a local stock with a long history of occurrence in the warm-temperate region of the south-western Atlantic. While intertidal mussel beds from the south-western Atlantic are ecologically similar in appearance, their assembly involves components clearly differentiated in terms of historical biogeography and phylogeny.

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.

Opheliidae (Polychaeta) from the Southwestern Atlantic ocean, with the description of Travisia amadoi n. sp., Ophelina gaucha n. sp. and Ophelina alata n. sp

Opheliid polychaetes belonging to the genera Armandia, Ophelia, Ophelina, and Travisia, collected along the Southwestern Atlantic coast off Brazil and Argentina, are recorded or given extended descriptions. Travisia amadoi sp. n., Ophelina gaucha sp. n. and Ophelina alata sp. n. are described.

Food consumption by the cock fish,Callorhynchus callorhynchus (Holocephali: Callorhynchidae), from Patagonia (Argentina)

SynopsisFood consumption by the holocephalanCallorhynchus callorhynchus, the ‘cock fish’, was studied in the northern San Matías Gulf, Argentine Patagonia. Relative gut fullness was assessed objectively with reference to estimated maximum fullness. Analysis of stomach contents of samples from the commercial catch shows maximum gut fullness during the spring. No diel cycle in gut fullness could be detected in the course of an experimental survey. Rate of gastroenteric emptying was estimated on board a research vessel by sacrificing at varying time periods fish kept in circulating sea water. Daily consumption rate by an adult fish of average size was estimated to be 1.4% of its body weight, very close to figures estimated for elasmobranchs from cold temperate waters; this is the first estimation of consumption rate by a holocephalan. Approximately half of the cock fish diet is composed of scallops, including the commercially importantAequipecten tehuelchus. It was calculated that consumption of this species in the study area reaches 81 metric tons per month, which corresponds to 5–7% of its estimated natural mortality.

Spionid polychaetes (Annelida: Spionidae) boring into shells of molluscs of commercial interest in northern Patagonia, Argentina

Abstract Six native bivalves of commercial interest, Aequipecten tehuelchus, Mytilus sp., Aulacomya atra, Ostrea puelchana, Protothaca antiqua and Pododesmus rudis, were examined on account of shell-boring spionid polychaetes in northern Patagonia, Argentina. Adults of Polydora rickettsi were found boring into shells of all molluscs but Mytilus sp., whereas Dipolydora cf. giardi was found only in shells of A. atra. The intensity of infestation of molluscs was low, and the prevalence of infestation by P. rickettsi varied from 20 to 54%, depending on the host species. Both boring spionids are reported for the first time from the Patagonian coast, and also as shell-borers of the examined molluscs.

Shell damage in the Tehuelche scallop Aequipecten tehuelchus caused by Polydora rickettsi (Polychaeta: Spionidae) infestation.

The different types of shell damage caused to the commercially valuable Tehuelche scallop (Aequipecten tehuelchus) by the polychaete Polydora rickettsi are described. X-rays, computerized tomography, shell sections, scanning electron microscopy, Energy Dispersive X-ray analysis (EDAX), mineralogical analyses and geometric morphometrics were applied to that end. Scallop shells presented three types of damage: (1) spots, (2) calcareous alterations, and (3) mud blisters. Microstructural alterations consisted of a simple conchiolin membranous layer in the case of spots, a series of interleaved layers of different degree of calcifications in calcareous alterations, and two different surface morphologies (muddy and mucous layers) in mud blisters. Damage was localized mainly along concentric growth rings, coincidentally with the location of most burrows, as shown by X-ray. Mineralogical analysis showed that in all cases (including non-infested shells) calcite was the calcium carbonate polymorph present. Geometric morphometrics showed that only 5% of shape variation was explained by infestation with P. rickettsi, irrespective of the type of damage. Number of worms per infested shell varied significantly among four beds. Left shells (upward-oriented) were significantly more affected than right shells, which are in closer contact with the bottom.

Scorched mussels (Brachidontes spp., Bivalvia: Mytilidae) from the tropical and warm-temperate southwestern Atlantic: the role of the Amazon River in their speciation.

Abstract Antitropicality is a distribution pattern where closely related taxa are separated by an intertropical latitudinal gap. Two potential examples include Brachidontes darwinianus (south eastern Brazil to Uruguay), considered by some authors as a synonym of B. exustus (Gulf of Mexico and the Caribbean), and B. solisianus, distributed along the Brazilian coast with dubious records north of the intertropical zone. Using two nuclear (18S and 28S rDNA) and one mitochondrial gene (mtDNA COI), we aimed to elucidate the phylogeographic and phylogenetic relationships among the scorched mussels present in the warm‐temperate region of the southwest Atlantic. We evaluated a divergence process mediated by the tropical zone over alternative phylogeographic hypotheses. Brachidontes solisianus was closely related to B. exustus I, a species with which it exhibits an antitropical distribution. Their divergence time was approximately 2.6 Ma, consistent with the intensification of Amazon River flow. Brachidontes darwinianus, an estuarine species is shown here not to be related to this B. exustus complex. We suspect ancestral forms may have dispersed from the Caribbean to the Atlantic coast via the Trans‐Amazonian seaway (Miocene). The third species, B rodriguezii is presumed to have a long history in the region with related fossil forms going back to the Miocene. Although scorched mussels are very similar in appearance, their evolutionary histories are very different, involving major historical contingencies as the formation of the Amazon River, the Panama Isthmus, and the last marine transgression.

The Patagonian Challenge: Melding Conservation with Development

Patagonia, at the southern tip of South America (Figure 17.1), is a region of over one million km2 shared by Chile and Argentina, endowed with some of the wildest landscapes in the world. Although remote and sparsely populated, Patagonian ecosystems are not pristine—most of them have been significantly disturbed by human activities. As is the case with much of Latin America, Patagonia is experiencing a push for economic development that is imposing ever increasing strains on natural resources.