File:American malacological bulletin (1987) (17533779904).jpg

English: locations of juvenile mussels collected at Big Moccasin Creek, Virginia

Title: American malacological bulletin
Identifier: americanmal4519861987amer (find matches)
Year: 1983 (1980s)
Authors: American Malacological Union
Subjects: Mollusks; Mollusks
Publisher: (Hattiesburg, Miss. ?) : (American Malacological Union)
Contributing Library: Smithsonian Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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NEVES AND WIDLAK: JUVENILE MUSSEL ECOLOGY 3 Using the area-density method, we multiplied mean densities of juveniles in each habitat type by total area of that type to estimate abundance (Everhart ef a/., 1975). Numbers per habitat type were summed to estimate total number of juveniles. A survival estimate of juveniles of all species com- bined was calculated using the relative abundance of each juvenile cohort (ages 0-3 years) in the 75 quantitative samples, according to the Robson and Chapman method (Ricker, 1975). RESULTS We collected 17 juvenile mussels in the 16 preliminary samples. Sphaeriids were common in all samples but juvenile mussels occurred only in samples from riffles and runs. Later quantitative samples collected from March 1983 to March 1984 differed in the occurrence of juveniles among habitat types, although some were taken in all habitats sampled. Totals of 75 juvenile and 36 adult mussels were collected in the 75 quantitative samples taken on the nine sampling dates (Table 1). Juveniles were present in only 30 of the 75 samples and were clumped in distribution (Fig. 1). For example, 18 of the juveniles taken behind boulders were in 2 of the 15 samples from this microhabitat. Sphaeriids were relatively common in all samples and occurred, in order of decreasing abundance, in the pool, runs, behind boulders, along banks, and riffle habitats. Three species of fingernail clams were identified: Pisidium com- pressum Prime, P. casertanum (Poli), and Sphaerium striatinum (Lamarck). A clumped distribution of sphaeriids was also evident but no distributional analysis by species among habitat types was attempted. Table 1. Number, age group, and location of mussels collected in 75 quantitative samples from Big Moccasin Creek on nine sampling dates, May 1983 to March 1984. HABITAT JUVENILE AGE GROUPS (yrs) ADULTS TOTAL 0 12 3 Total Juveniles >4 Pool 0 4 3 1 8 0 8 Run 4 3 3 1 12 7 19 Riffle 5 6 3 3 17 13 30 Boulder 15 6 7 7 35 8 43 Bank 110 1 3 8 11 TOTAL 25 20 16 14 75 36 111 Because juvenile mussels and sphaeriids showed a clustered distribution, and sampling covered only a small frac- tion of total habitat, our computed estimates of bivalve den- sities are considered to be only rough approximations (Table 2). Densities (no./m2) based on sampling results ranged from 0 to 52 juveniles in riffles, pools, and runs; 0 to 17 along stream banks; and 0 to 175 behind boulders. The wide ranges reflect the apparently clustered distribution of this life history stage. Of the 92 juvenile mussels collected in qualitative and quantitative samples from BMC, 69 were less than 15 mm long (range 0.8 - 30.3 mm). Identifications were as follows; 50 Villosa spp., 34 Medionidus conradicus and 8 Fusconaia barnesiana or Pleurobema oviforme. Four age classes (0-3) were identified, with slightly more specimens in age classes 0 and 1 (Table 3). Mean lengths of juveniles ranged from 2.7 mm for age 0 to 23.2 mm for age 3. Age 0 individuals were most commonly collected behind boulders and were absent POOL
Text Appearing After Image:
Flow • 1 3 2 • RF = RIFFLE RN = RUN B = BOULDER S = STREAMSANK Fig. 1. Location of samples, and the number and location of juvenile freshwater mussels collected at the study site in Big Moccasin Creek. Numbers indicate number of juveniles collected at that location; • represents sample locations without juveniles; S and B identify microhabitat samples along streambanks and behind boulders, respectively.

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