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Freshwater Pearl Mussel (freshwater + pearl_mussel)
Selected AbstractsTiming of spawning and glochidial release in Scottish freshwater pearl mussel (Margaritifera margaritifera) populationsFRESHWATER BIOLOGY, Issue 12 2003Lee C. Hastie Summary 1. The timing of reproduction was investigated in six Scottish freshwater pearl mussel populations from 1993 to 2002. Gravid females were examined and the release of mussel larvae (glochidia) was monitored. 2. Annual spawning (oviposition) and spat (glochidial release) events occurred during June to July and June to September, respectively. 3. Between-river differences in timing seem to be related to water temperature. Mussels in the warmest rivers tend to spawn and spat first, and vice-versa. 4. Thermal variations also seem to influence the timing of reproduction within rivers, which can be delayed by several weeks during cold years. At least 3000°-days occur between annual episodes of glochidial release. 5. The timing of spawning is determined gradually, probably by a thermal summation effect. 6. The release stage occurs as a sudden, synchronised event, with most of the glochidia spat over 1,2 days, indicating that it is triggered by an environmental cue. Sudden changes in water temperature and/or river level often result in spats, and the underlying mechanism may be respiratory. [source] Effects of integrated combination and quicklime supplementation on growth and pearl yield of freshwater pearl mussel, Hyriopsis cumingii (Lea, 1852)AQUACULTURE RESEARCH, Issue 14 2009Yan Wang Abstract The effects of integrated combination and quicklime supplementation on growth and pearl yield of a freshwater mussel, Hyriopsis cumingii (Lea, 1852), were examined through a 137-day growout in land-based enclosures. The integrated combinations examined were either mussel, bighead carp and gibel carp or mussel and bighead carp. Each combination was treated either with or without quicklime supplementation. One half of the mussels in each enclosure were grafted with pieces of the mantle epithelium while the other half were not. During the experiment, gibel carp were fed formulated feed while the mussel and bighead carp were fed natural live food. Quicklime was regularly provided in the enclosures as calcium replenishment. The species composition in the integrated system significantly affected growth in shell size and wet weight of the mussels regardless of the graft and pearl yield, while no significant effects of quicklime supplementation were detected. Growth rates in shell size and wet weight of both grafted and non-grafted mussels and pearl yield were slightly higher in the enclosures with mussel, bighead carp and gibel carp than those with mussel and bighead carp, although these differences were not statistically significant. The non-grafted mussel exhibited faster growth in shell size and wet weight than the grafted mussel within the same treatment. Results of the present study indicate that species combination in an integrated system can affect growth and pearl yield of H. cumingii. The species combination of mussel, bighead carp and gibel carp is recommended for commercial H. cumingii farming. [source] Characterization of freshwater pearl mussel (Margaritifera margaritifera) riverine habitat using River Habitat Survey dataAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 3 2003L.C. Hastie Abstract 1.The feasibility of using River Habitat Survey (RHS) data to describe freshwater pearl mussel (Margaritifera margaritifera) macrohabitat in the River Spey, north-east Scotland, was investigated. 2.Mussels were found to be positively associated with a number of RHS variables. These included: boulder/cobble river bed substrates, broken/unbroken standing waves (channel flow types), aquatic liverworts/mosses/lichens and broadleaf/mixed woodland/bankside tree cover. Negative associations with gravel-pebble/silt substrates and emergent reeds/sedges/herbs were also found. 3.Two binary logistic regression models, based on seven and four variables, respectively, were constructed in order to predict the presence/absence of mussels at any given site. Predictive success rates of 83% and 78% were achieved. 4.Another binary logistic regression model, based on four variables, was constructed in order to predict the occurrence of ,optimal' M. margaritifera habitat (overall mussel densities , 1 m,2). A predictive success rate of 83% was achieved. 5.The results indicate two potentially important applications of RHS for the conservation management of M. margaritifera: (1) for monitoring the effects of physical changes on extant mussel beds (and predicting their effects on mussel populations), and (2) for determining the habitat suitability of historically occupied sites for re-introductions. Copyright © 2003 John Wiley & Sons, Ltd. [source] EVALUATING CONTEMPORANEITY AND POST-MORTEM AGE OF MALACOLOGICAL REMAINS USING SCLEROCHRONOLOGY AND DENDROCHRONOLOGY*ARCHAEOMETRY, Issue 5 2009S. HELAMA Sclerochronology and dendrochronology are based on series of incremental skeletal and cambial growths that have been correctly aligned in time via cross-dating (i.e., incremental dating through synchronization of the growth variability on a visual and statistical basis). Here we report a study of the shell increments of two anthropogenic death assemblages of freshwater pearl mussel (Margaritifera margaritifera) originating from Finnish Lapland. First, we cross-dated a new sclerochronology from an assemblage of river pearl mussel shells with unknown post-mortem age. Second, this chronology was cross-dated with the previously published sclerochronology of the same species and geographical source. Third, the composite of the two sclerochronologies was compared to dendrochronologies from Lapland. Temporal association of the two types of chronologies was markedly high, as confirmed by t -values of 7.1 and 8.9, which are well above the acceptable limit of 3.5. Our study demonstrates the potential of sclerochronological and dendrochronological materials and techniques in assessing the contemporaneity (i.e., temporal overlap) and post-mortem age of archaeomalacological deposits. In the palaeontological context, these results also show the wider possibility of dating shells with a large number of annual increments from natural deposits. [source] | ||||||||||