Concholepas

Abstract: Marine mollusks are among the most importantinvertebrate fisheries in the world. The mainclasses of mollusk fished are Cephalopoda,Bivalvia and Gastropoda. Marine gastropodsrepresent approximately 2% of the mollusksfished in the world. Several species ofgastropods, such as Haliotis spp., Strombus spp., Busycon spp. and Concholepas concholepas, have high economicvalue in international markets and playimportant social roles in small-scale artisanalfisheries. In the past 25 years wild-stockcatches of marine gastropods have increasedfrom 75,000 mt in 1979 to 103,000 mt in 1996.During the same period the countries involvedin gastropod landings rose from 23 to 47.Gastropods are fished mainly in: (1) theAmerican continent, dominated by the extractionof the muricid ``loco'', C. concholepas, inChile and Peru; strombid conchs, Strombusspp., in the Caribbean, and abalone, Haliotis spp., in California and the west coastof the Baja California peninsula; (2) Asia andOceania, with the dominate abalone fishery,mainly in Australia and New Zealand, and thehorned turban snail, Turbo truncatus, inJapan and Korea; (3) in Africa and Europe, thedominate species extracted are Haliotismidae, heavily fished in South Africa, and thecommon periwinkle, Littorina littorea,and the whelk Buccinum undatum, which areextracted in Europe. This review summarizes the fishery of abalonespecies in California and the west coast of theBaja California peninsula. We highlightoverfishing situations and the utilization ofadaptive management tools, such as those inoperation in Baja California, where small-scalefisher associations (cooperatives) havereceived exclusive access rights to abaloneextraction within specific fishing zones, since1936. We also review the abalone fishery inAustralia, and the use of IndividualTransferable Quotas (ITQs) and Total AllowableCommercial Catches (TACC), which have been inuse since the mid-1980's. We describe thegastropod fisheries in Chile, mainly C. concholepas, highlighting their economic andsocial importance. We provide information onthe evolution of catches and exports anddiscuss the development of novel managementadaptive tools, such as the implementation ofthe Benthic Regime for Extraction andProcessing (BREP), the introduction ofNon-Transferable Individual Quotas (NTIQs) andterritorial users rights for benthic fisheries,such as the Management and Exploitation Areas(MEAS). Finally, we present and discuss thenecessary steps for the sustainable managementof marine gastropods and other benthic resources.

Abstract: The coast of central Chile is characterized by the occurrence of coastal upwelling during the austral spring and summer seasons, which probably has important consequences for the cross-shelf transport of larval stages of many species. Three cruises were conducted off the locality of El Quisco during upwelling-favorable wind periods to determine the surface distribution of epineustonic competent larvae of the gastropod Concholepas concholepas during such events. Contrary to the predictions of a traditional model, where neustonic-type larvae are transported offshore under such conditions, competent larvae of this species were exclusively found in the area between the shore and the upwelling front. Two additional cruises were conducted during calm periods to determine diel variation in the vertical distribution of C. concholepas competent larvae. The absence of competent larvae at the surface during early night hours suggests a reverse vertical migration. Thus, the retention of C. concholepas competent larvae in the upwelled waters could be the result of the interaction between their reverse diel vertical migration and the typical two-layer upwelling dynamics.

Abstract: In this paper we document the changes experienced by the carnivorous Concholepas concholepas snail population after the establishment of a marine reserve in May 1978. Our data indicate that the release from human predation results in a striking change of the Concholepas population structure, due to the increment of individuals larger than 40-50 mm peristomal length. This evidence strongly indicates that the usual absence of larger size classes from the intertidal is not a consequence of physiological limitations of the muricid, as was previously thought. Significant density differences were detected only in 1984, but they were due to substantial reduction of the snails in the harvested control area.

Abstract: Theoretical and empirical ecologists have long acknowledged that information about the intensity or strength of the interaction between species is crucial for an understanding of community dynamics. In communities in which predation is an important structuring process, and some predator species are commercially exploited, quantitative estimates of predation by different predator species within a guild are necessary to make even the simplest recommendations about conservation and resource management. Here, we evaluated per capita and population level components of predation intensity of three intertidal predators that feed on monospecific stands of barnacles and mussels at wave exposed sites in the rocky intertidal zone of central Chile. These prey species represent the two most distinctive stages of the mid-intertidal seascape, with mussels being competitively dominant. Our results showed that the commercially exploited gastropod Concholepas concholepas and the sea star Heliaster helianthus have similarly large per capita and population effects on the competitively dominant mussel Perumytilus purpuratus. Their per capita (by average size individual) and population effects on mussels were more than two orders of magnitude larger than those of Acanthocyclus gayi crabs and likely even larger than the effect of other predator species in this system (other crabs, whelks, birds, fish). The overall pattern of predation on barnacles was similar to that on mussels, but some differences occurred in the way different components of predation intensity were distributed across predator species. Despite the roughly similar pattern of population predation intensity between prey species, the expected consequences for the prey population, and hence the rest of the community, were acutely different for mussels and barnacles.