Astacoides

Abstract: Hobbs, Horton H., Jr. A Review of the Crayfish Genus Astacoides (Decapoda: Parastacidae). Smithsonian Contributions to Zoology, number 443, 50 pages, 23 figures, 1987.—The crayfish fauna of Madagascar consists of six species belonging to the endemic genus Astacoides. Four of them, originally recognized as varieties of a single species Astacoides madagascarensis and subsequently accorded subspecific status, are elevated to specific rank. Two, A. crosnieri and A. petiti, are described as new. Following remarks on the limited range of the genus, which appears to be confined to higher elevations in the eastern part of the island between 18° and 25° South latitude and 46° to 49° East longitude, are notes on the organization of the text and a resume of our previous knowledge of the genus. This is followed by discussions of the taxonomic characters considered in the study, the common origin of the disjunct Astacoides with other parastacid stocks, and the evolution and interrelationships of the Madagascan species. A diagnosis of the genus accompanies a key provided for the recognition of its members. A synonymy, diagnosis, description, statement of range, list of localities and specimens examined, and illustrations are provided for each species. OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded in the Institutions annual report, Smithsonian Year. SERIES COVER DESIGN: The coral Montastrea cavernosa (Linnaeus) Library of Congress Cataloging in Publication Data Hobbs, Horton Holcombe, 1914A review of the crayfish genus Astacoides (Decapoda: Parastacidae) (Smithsonian contributions to zoology ; no. 443) Bibliography: p. I. Astacoides—Classification. 2. Crustacea—Classfication. 3. Crustacea—Madagascar Classification I. Title. II. Series. QL1.S54 no.443 [QL444.M33] 591s 86-13093 [595.3'841]

Abstract: SUMMARY 1 Freshwater crayfish of the genus Astacoides are endemic to the highlands of eastern Madagascar Very little is known about their ecology and how this affects their vulnerability to threats Working in the Fianarantsoa forest corridor, we used a combination of ecological research (>29 000 crayfish caught and released) and interviews (>130 interviews in 38 villages) to investigate the ecology and status of four of the seven described species 2 Astacoides species studied showed very slow growth, with growth rates of Astacoides granulimanus and Astacoides crosnieri among the slowest known in any species of crayfish We found individuals of all three species for which we had growth data which we estimate at more than 20-years old The size at which females became ovigerous varied among species Astacoides betsileoensis withheld reproduction until a large size (only 30% of females were gravid at 60-mm carapace length, compared with 90% for A granulimanus) This is likely to make A betsileoensis particularly vulnerable to overexploitation and we found that only 10% of individuals measured in a market (n ¼ 909) would have reproduced before being caught compared with 35% of the more common A granulimanus (n ¼ 30 561) 3 Habitat loss is a serious threat to the genus; even A granulimanus, the most widespread species, was only found in rivers or streams flanked by natural vegetation Astacoides caldwelli, the rarest species in this study, was found only at low altitudes (<800 m) in rivers draining forested catchments Habitat loss is particularly rapid in low elevation forest A crosnieri was restricted to swampy land that is rapidly being converted to rice fields Introduced Asian snakehead fish (Channa maculata) may pose a hitherto unrecognised threat to some species, particularly A betsileoensis 4 Madagascar’s freshwater habitats have great significance for global biodiversity yet conservation effort, as in much of the world, has focused on terrestrial ecosystems Until recently almost nothing was known about the ecology of Astacoides crayfish, a diverse and economically important genus Here, we show that members of the genus vary markedly in their reproductive biology, growth rates, habitat requirements and the threats they face We suggest that habitat loss is an urgent threat, especially to A caldwelli and A crosnieri,

Abstract: Madagascar's endemic freshwater crayfish (Parastacidae: Astacoides) are harvested by local people for both subsistence use and small-scale trade. There has been concern that populations, and even species, are threatened by overexploitation but little is known about the harvest or its economic importance. We studied crayfish exploitation in eastern Madagascar over 3 years. The existence of local taboos (fady) preventing commercial crayfish harvesting, as well as access to markets and forest, influenced involvement in the harvest. All four crayfish species found in the region were harvested, but A. granulimanus provided the majority of the catch. In one harvesting village more than 50% of the 47 households were directly involved in the harvest, which contributed USD 2,382 to the village economy in 2003/2004, an important sum in the context of local incomes. Subsistence use was widespread, particularly by children to whom it may provide an important protein source. Community-based conservation (through transfer of harvesting rights and responsibilities for forest management to local communities) is central to a new conservation paradigm in Madagascar. This recognizes communities' long term interest in their natural resources and offers an ideal opportunity for those concerned with the sustainability of the harvest to implement management tools (such as avoiding reproductive females, size limits and no-take zones). We discuss each tool with respect to biological implications and practical constraints. We note that community-based approaches may not be sufficient to conserve rarer species, which make up a small proportion of the value of the harvest.

Abstract: A new species of crayfish, Astacoides hobbsi , is the seventh recognized in the endemic Madagascan genus Astacoides Guerin-Meneville, 1839 and is described from four male specimens collected in the Andranofotsiorana effluent of the river Ranomadio (Fianarantsoa province). The new species can be distinguished from all congeners by a combination of limited carapace spination, pale white color, gill formula of 13 + epr + 5r, lack of bullar lobes on sternite XIII, laterally curved lateral processes on sternite XIII, and spination of third maxilliped merus and ischium. The new species co-occurs with three other Astacoides species ( A . granulimanus Monod & Petit, 1929, A . caldwelli (Bate, 1865), and A . betsileoensis Petit, 1923) in the same stream system. Special consideration should be given to conservation of this new species, as it is the Astacoides species known from the fewest specimens and may have a very restricted distribution.