Distribution and Association of Larval Crabs (Decapoda: Brachyura) on the Scotian Shelf

Abstract

Roff, I. C., L. P. Fanning, and A. €3. Stasko. 1986. Distribution and association d larval crabs (Decapoda: Brachyura) on the Scstian Shelf. Can. 1. Fish. Aquat. Ssi. 43: 587-599. Thirty-five taxa of weustonic larval Brachyura were distinguished and identified to stage of development in 3055 samples from the Scotian Shelf taken from north of Cape Breton to Georges Bank. A maximum of 17 species of larvae was taken in a single tow, with a norm of about 4 per tow. The most abundant species, collected in all stages sf development, were the indigenous Chionoecetes opilio, Hyds araneus and Hyas coarctatus, Cancea borealis and Cancea irroaatus, and Carcinus maenas. Biomass was dominated by the Hyas and Cancer species.Distributions sf the three Majidae species indicated that larvae drift southwest along the shelf, and that they are indigenously derived. Twenty-six expatriate species occurred as megalspas only, predominantly offshore. Reciprocal averaging and factor analysis showed that there was considerable separation of the indigenous and expatriate larval species, but did not reveal strong relationships to environmental variables or ecslogical gradients. Recurrent group analysis indicated that community structure was weak and variable, but confirmed the virtual separation into indigenous and expatriate associations. An examination of co-occurrences of indigenous and expatriate species by stage sf development showed strong patterns. We suggest that concurrent analysis of larval lobster and larval crab distribution patterns on the Scotian Shelf could indicate recruitment origin of lobsters (Homaaus americanus). Trente-cinq taxa de Brachykara neustonique larvaire ont ete distingues et identifies jusqu'au stade de developpernent dans 3 055 6chantillsns preleves sker la plate-forme Scstian entre la partie nord du Cap-Breton et le banc de Georges. Au maximum 17 especes de larves snt ete prises en un seul coup de filet, avec une moyenne de 4 par ramassage. Les especes les plus abondantes, recueillies 3 tous les stades de d6veloppemewt, etaient: Chionoecetes opiiio, Hyas araneus et Hyas coarctatus, Cancer borealis et Cancer irroaatus, et Carcinus maenas. Hyas et Cancer etaient les especes dominantes dans la biornasse. L'analyse des distributions des trois esgeces de Majidae a revele que les larves se dkplacent vers le sud-suest le long de la plate-forme continentale et qu'elles sont d'origine indigene. Vingt-six especes expatriees ont kt6 trouvkes sous forme de mkgalopes seulement, surtout au Barge. Le calcul de la moyenne des inverses et I'analyse factsrielle snt montre que la separation etait considerable entre les especes larvaires expatriees et indigenes mais qu'il n'existait pas d'irnportantes relations avec des variables ewvironwernentales et des gradients ecologiques. L'analyse des groupes recurrents a indiqu6 que la structure de la cornmunaute etait faible et variable mais qu'il y avait bien separation virtkaelle en associations indigene et expatriee. Un examen de la co-occurrence des especes indighes et expatriees pa...

Composition and distribution of zooplankton across an upwelling front on the northern Portuguese coast during summer

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A simple range expansion model of multiple pathways: the case of nonindigenous green crab Carcinus aestuarii in Japanese waters

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“…this behaviour occurs even in larvae that were never subjected to tidal influences during embryonic and ontogenic developments (Zeng & Naylor 1996d). Available evidence suggests that larvae develop in shelf waters (Rees 1955, Roff et al 1986, Lindley 1987, Queiroga 1996) over 4 to 10 wk depending on temperature (Dawirs 1985, Mohamedeen & Hartnoll 1989, Nagaraj 1993. The megalopa is the stage that reinvades estuaries.…”