المؤلفون: Thieltges, David¹ dthieltges@awi-bremerhaven.de

المصدر: Hydrobiologia. Apr2006, Vol. 559 Issue 1, p455-461. 7p. 2 Black and White Photographs, 3 Graphs.

مصطلحات موضوعية: *NUTTALL cockle, *AQUATIC animals, *DEATH (Biology), *MORTALITY, *POPULATION, *PARASITES, *TIDAL flats, *WETLANDS, *AQUATIC biology

مستخلص: In late summer 2004, a conspicuous cockle ( Cerastoderma edule) mortality event was observed on a tidal flat in the northern Wadden Sea (North Sea, Germany) with many fresh valves and still living cockles lying on the sediment surface. To investigate whether trematode parasites utilizing the cockle as first or second intermediate host were involved in this mortality, buried and surfaced cockles were sampled and analyzed, and a laboratory experiment conducted. The field survey showed no statistical difference in intensity of parasites encysted in the foot of cockles. Three species of Himasthla utilizing the cockle as second intermediate host and known to impair the cockle’s burrowing ability were found in buried cockles with 148.4±111.1 metacercariae/foot and in surfaced cockles with 164.2±84.4. There was also no difference in infection levels of parasites utilizing the cockles as second intermediate host in other cockle tissues between buried and surfaced cockles. In contrast, surfaced cockles showed a ten times higher prevalence (71.0%) than buried cockles (7.4%) of the trematode Gymnophallus choledochus – a parasite utilizing the cockle as first (and second) intermediate host – filling almost the entire body cavity and eliminating gonad structures. In an aquarium experiment of 14 days, all cockles found buried on the tidal flat survived compared to only 23.3% found on the surface. This suggests G. choledochus to be a castrating agent and a serious mortality factor in adult cockle populations. [ABSTRACT FROM AUTHOR]

المؤلفون: Teoh, H. W., Chong, V. C.

المصدر: Hydrobiologia; Feb2014, Vol. 723 Issue 1, p255-265, 11p

مصطلحات موضوعية: SPAWNING, HERMIT crabs, ESTUARINE animals, MORTALITY, PREDATION, COCKLE fisheries, CRUSTACEA

مستخلص: Two species of sympatric hermit crab, Diogenes moosai Rahayu & Forest, 1995 and D. lopochir Morgan, 1989, spatially defined in the Matang mangrove estuary, and facing high mortality due to tidal emersion, predation and competition are hypothesised to adopt different reproductive strategies for successful recruitment. The crabs were sampled by a small otter trawl at mid-estuary, river mouth, mudflat and shoal area along the estuary to adjacent coastal area. Diogenes moosai was widespread in the mudflat as well as in the subtidal shoal area where D. lopochir was dominant. Diogenes moosai showed year-round reproduction, whereas D. lopochir a discontinuous spawning pattern. Major reproduction in both species, however, occurred in January/February and July which resulted in two major recruitment pulses in a year. Diogenes moosai also suffered very high mortality resulting from cockle harvesting on the mudflat, twice that of D. lopochir. Our results show that the more widespread species at higher risk of exposure to extreme physical conditions (in the mudflat), predation and competition for shell resources, generally spreads its reproduction over the year, while the dominantly subtidal species at greater risk of predation only reproduces less regularly but at the most favourable period. [ABSTRACT FROM AUTHOR]

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المؤلفون: Ving Ching Chong, H. W. Teoh

المصدر: Hydrobiologia. 724:255-265

مصطلحات موضوعية: geography, education.field_of_study, geography.geographical_feature_category, Ecology, media_common.quotation_subject, Population, Shoal, Estuary, Aquatic Science, Biology, Hermit crab, biology.organism_classification, Competition (biology), Predation, Fishery, Cockle, Mangrove, education, media_common

الوصف: Two species of sympatric hermit crab, Diogenes moosai Rahayu & Forest, 1995 and D. lopochir Morgan, 1989, spatially defined in the Matang mangrove estuary, and facing high mortality due to tidal emersion, predation and competition are hypothesised to adopt different reproductive strategies for successful recruitment. The crabs were sampled by a small otter trawl at mid-estuary, river mouth, mudflat and shoal area along the estuary to adjacent coastal area. Diogenes moosai was widespread in the mudflat as well as in the subtidal shoal area where D. lopochir was dominant. Diogenes moosai showed year-round reproduction, whereas D. lopochir a discontinuous spawning pattern. Major reproduction in both species, however, occurred in January/February and July which resulted in two major recruitment pulses in a year. Diogenes moosai also suffered very high mortality resulting from cockle harvesting on the mudflat, twice that of D. lopochir. Our results show that the more widespread species at higher risk of exposure to extreme physical conditions (in the mudflat), predation and competition for shell resources, generally spreads its reproduction over the year, while the dominantly subtidal species at greater risk of predation only reproduces less regularly but at the most favourable period.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::0ff0c2742dcc7df9af6c1fc1ca2fde86Test
https://doi.org/10.1007/s10750-013-1738-8Test

المؤلفون: Islay D. Marsden, S. R. Maclaren

المصدر: Hydrobiologia. 649:217-229

مصطلحات موضوعية: Biomass (ecology), geography, geography.geographical_feature_category, biology, Ecology, Estuary, Aquatic Science, biology.organism_classification, Fishery, Austrovenus stutchburyi, Benthos, Algal mat, Aquatic plant, Cockle, Sea lettuce

الوصف: Macroalgal mats occur seasonally in many estuaries worldwide but there is little information on their short- or long-term effects on the abundance or resilience of macrofauna. Within a small estuary, with a history of exposure to algal mats (Avon-Heathcote Estuary, Christchurch, New Zealand), we quantified the relationship between macroalgal mats and community composition. There was a high degree of species overlap between sites, and community analysis did not separate out areas that had been previously exposed to mats. Density of the cockle Austrovenus stutchburyi was negatively correlated with current abundances of sea lettuce Ulva and the red alga Gracilaria chilensis. A caging experiment at three sites with different sediment characteristics investigated the survival of the cockle (A. stutchburyi) to short-term exposure to mats of Ulva sp. and G. chilensis. Neither low or high algal biomass had any effect on cockle mortality, macroinvertebrate diversity or the sediment characteristics. Although the population structure of cockles differed amongst sites, bivalves followed normal seasonal development, regardless of the experimental treatment. The results confirm that the cockle has the ability to survive short-term exposure to algal mats.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::b64bbf34a96835a867e4254c5c1eb473Test
https://doi.org/10.1007/s10750-010-0249-0Test

المؤلفون: David W. Thieltges

المصدر: Hydrobiologia. 559:455-461

مصطلحات موضوعية: Fishery, Cerastoderma edule, biology, Intermediate host, Parasite hosting, Zoology, Parasitism, Aquatic Science, Trematoda, Cockle, biology.organism_classification, Bivalvia, Mollusca

الوصف: In late summer 2004, a conspicuous cockle (Cerastoderma edule) mortality event was observed on a tidal flat in the northern Wadden Sea (North Sea, Germany) with many fresh valves and still living cockles lying on the sediment surface. To investigate whether trematode parasites utilizing the cockle as first or second intermediate host were involved in this mortality, buried and surfaced cockles were sampled and analyzed, and a laboratory experiment conducted. The field survey showed no statistical difference in intensity of parasites encysted in the foot of cockles. Three species of Himasthla utilizing the cockle as second intermediate host and known to impair the cockle’s burrowing ability were found in buried cockles with 148.4±111.1 metacercariae/foot and in surfaced cockles with 164.2±84.4. There was also no difference in infection levels of parasites utilizing the cockles as second intermediate host in other cockle tissues between buried and surfaced cockles. In contrast, surfaced cockles showed a ten times higher prevalence (71.0%) than buried cockles (7.4%) of the trematode Gymnophallus choledochus – a parasite utilizing the cockle as first (and second) intermediate host – filling almost the entire body cavity and eliminating gonad structures. In an aquarium experiment of 14 days, all cockles found buried on the tidal flat survived compared to only 23.3% found on the surface. This suggests G. choledochus to be a castrating agent and a serious mortality factor in adult cockle populations.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::cecd13cacdf5af76be2894d599c97dd5Test
https://doi.org/10.1007/s10750-005-1345-4Test

المؤلفون: C. A. Burton, M. M. Learmouth, J. T. MacMillan

المصدر: Hydrobiologia. 465:1-5

مصطلحات موضوعية: Cerastoderma edule, biology, Ecology, business.industry, Mussel, Aquatic Science, Pacific oyster, biology.organism_classification, Fishery, Aquaculture, Cockle, Ostrea edulis, business, Mollusca, Shellfish

الوصف: There are six main species of shellfish of commercial importance within the UK (mussels, flat oysters, cockles, king scallops, Manila clams and lobsters) which can be thought of as ranched to varying degrees. A seventh (Pacific oysters) can be included, since a very small proportion of the production may undergo a period of growth on natural habitats in some areas. An eighth species (Palourdes or native clams) appeared in the statistics for the first time in a number of years in 1998. Seafish, as part of its role in promoting the sustainable management of resources, has examined the current state of the shellfish aquaculture industry in the UK.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::f165aac104aa6ae8693566566c7574fdTest
https://doi.org/10.1023/a:1014509412045Test

المؤلفون: A.G. Brinkman, A. Meijboom, E.M. Dijkman, N.M.J.A. Dankers

المصدر: Hydrobiologia. 465:21-30

مصطلحات موضوعية: biology, Ecology, Fauna, Intertidal zone, Mussel, Aquatic Science, Bivalvia, biology.organism_classification, Fishery, Habitat, Environmental science, Cockle, North sea, Mollusca

الوصف: In the Waddensea, musselbed distribution and abundance has decreased. Management is aiming at increase of area of beds. Fisheries have been regulated. Mussel beds are slowly recovering, and localities where recovery occurs can be predicted reasonably well. Active restoration of beds has not been necessary, as long as newly formed beds are protected from fisheries. Potential suitable sites should be protected from bottom-disturbing activities which might influence the substrate for spatfall such as cockle beds and tube-building polycheates.

الوصول الحر: https://explore.openaire.eu/search/publication?articleId=doi_________::3a1e90a5c0ee9a719e464d8cca5a83e2Test
https://doi.org/10.1023/a:1014592808410Test