Dawson Blood chemistry of Scophthalmus aquosus in Long Island Sound 



431 



nated stations and held in running seawater aboard tiie 

 boat until blood samples were taken, generally within 



1 hour after the fish were collected. On occasion, be- 

 cause of inclement weather, it was necessary to return 

 to the laboratory and sample the fish at dockside; in 

 that case, the interval between capture and sampling 

 was up to 4 hours. 



The stations were sampled monthly unless inclement 

 weather or boat repairs precluded sampling. General- 

 ly, blood samples were taken from 20 fish at each sta- 

 tion; if fewer fish were obtained, sample numbers were 

 necessarily smaller. Of 102 collections used, 67 con- 

 sisted of 20 fish each, 33 of 10-19 fish, and one each 

 of 8 and 9 fish. Respective lengths of fish sampled at 

 Station 1, 2, and 3 were 26.7 ± 0.13, 25.0 ± 0.16, and 

 25.6 ±0.15 cm. Hematocrit (Hct), hemoglobin (Hb), 

 plasma osmolality, sodium, potassium, and calcium 

 were measured on each blood sample. Prior to each fish 

 collection, a bottom-water sample was collected for 

 measurement of temperature, salinity, and dissolved 

 oxygen. Four preliminary collections were made at 

 each station in 1979; intensive sampling continued from 

 May 1980 through April 1983. 



Exposure studies 



Windowpane flounder were exposed to mercury, cop- 

 per, or cadmium in the laboratory. Fish used in the 

 exposure studies were collected by otter trawl using 

 15- or 30-minute tows in the vicinity of Milford, Con- 

 necticut, and transported to the laboratory in running 

 seawater. They were held at the laboratory for at least 



2 weeks prior to exposure. In general, exposures were 

 conducted during the colder months when the fish do 

 not normally feed much. However, they were given 

 small amounts of minced surf clam Spisula solidissima 

 weekly. The fish measured 24.8 + 0.21 cm in length and 

 158.4 ± 4.2 g in weight. 



Three 60-day exposures were performed: the first 

 used HgClo at a nominal mercury concentration of 5 

 or 10 Mg/L. the second used CuClo-2H20 at a nominal 

 copper concentration of 10 or 20 ^g/L, and the third 

 used CdCl2-2V2H20 at a nominal cadmium concentra- 

 tion of 5 or 10 Mg/L. Measured concentrations were 

 5.1 + 0.60 ppb and 12.7 ± 2.20 ppb for low and high cad- 

 mium concentrations, and 19.2 ±1.4 for the high cop- 

 per concentration. Backgi'ound metal levels were below 

 1 uglL for mercury, below 5 juglL for copper, and below 

 1 (lig/L for cadmium. The fish were exposed in 285-L 

 fiberglass tanks filled to 225 L with sand-filtered Mil- 

 ford Harbor seawater by a proportional dilution ap- 

 paratus (Mount and Brungs 1967). The diluter con- 

 trolled the intermittent delivery of toxicant-containing 

 or control seawater at a flowrate of 1.5 L every 2.5 

 minutes throughout the exposure period. This provided 



a flow of 864 L per day and an estimated 90% replace- 

 ment time of 15 hours (Sprague 1969). The seawater 

 was at ambient salinity during the exposures. The 

 temperature was slightly above ambient because the 

 water was held in the heated building during filtration 

 and delivery. 



Duration of the mercury exposure was 22 December 

 1979-20 Febraary 1980. The salinity range diunng that 

 time was 25.0-26.9"Ain. Temperature in the exposure 

 tanks was 8°C at the beginning of the exposure, drop- 

 ping to 3-4 °C throughout most of the month of Febru- 

 ary when the exposure was completed. During the mer- 

 cury exposure, each tank held 5 fish for a total of 20 

 fish per concentration and 20 controls. 



The copper exposure ran from 7 January through 8 

 March 1983. Salinity during the exposure period was 

 24.4-26.4"/i«i. Temperature was 9°C at the beginning 

 of exposure, dropped to a low point of 6°C in mid- 

 February, and gradually rose to 9°C at the end. Three 

 tanks at each concentration held 4 fish per tank. 



Duration of the cadmium exposure was 27 January- 

 28 March 1984. Salinity range during that time was 

 22.6-25.9'7o„. Temperature was 6.5°C at the begin- 

 ning of the exposure, rising to 8.5 °C at the end. The 

 lowest temperature recorded was 5.0 °C on 3 February. 

 Twenty fish were exposed per concentration, 5 fish per 

 tank. 



Blood chemistry 



The parameters measured were hematocrit (Hct), 

 hemoglobin (Hb), mean corpuscular hemoglobin concen- 

 tration (MCHC), plasma osmolality, sodium, potassium, 

 and calcium. Erythrocyte counts (RBC) and calcula- 

 tions of mean corpuscular hemoglobin (MCH) and mean 

 corpuscular volume (MCV) were performed only on 

 animals used in exposures. 



Blood was collected from each animal by cardiac 

 puncture using a 3-mL plastic syringe and a 20- 

 or 22-gauge needle. The sample was transferred 

 gently into an 8-mL glass vial containing 150 units 

 of dried ammonium heparinate as an anticoagulant. 

 Immediately following collection of the last blood 

 sample, a portion of each blood sample was centri- 

 fuged at 12 000 g and the plasma frozen for later 

 determination of osmolality, sodium, potassium, and 

 calcium. The remaining whole-blood sample was used 

 for the determination of hemoglobin, hematocrit, and 

 erythrocyte counts. Hemoglobin was determined by the 

 cyanmethemoglobin method using Hycel chemicals. 

 Microhematocrits were determined following cen- 

 trifugation for 5 minutes at 13 500 g. Erythrocyte 

 counts were made in a hemacytometer; blood samples 

 were diluted 1:200 with Yokoyoma's solution (Katz 

 1950). Plasma osmolality was determined with an 



