FISHERY BULLETIN: VOL. 75, NO. 3 



death and stress to the zoeae of four species of 

 anomuran and six species of brachyuran crabs 

 acclimatized to natural ambient conditions. These 

 crabs constitute some of the more important types 

 in the littoral zone and include species important 

 in sport and commercial fisheries. Testing was 

 done at the National Marine Fisheries Service 

 facility at Mukilteo, Wash., from May to October 

 1971 and in February 1972. 



MATERIALS AND METHODS 



Ovigerous crabs were collected from the mid- 

 Puget Sound areas of Possession Sound, Poverty 

 Bay, and at Alki Point. Graceful crab, Cancer 

 gracilis, Dungeness crab, C. magister, and kelp 

 crab, Pugettia producta, were collected subti dally; 

 other species were taken on beaches during low 

 tides. The messmate crab, Pinnixa littoralis, was 

 collected inside horse clam, Tresus capax, that 

 had been excavated. Most of the experimental 

 species were ovigerous in May and June; the mud 

 flat crab, Hemigrapsus oregonensis, black clawed 

 crab, Lophopanopeus bellus, and porcelain crab, 

 Petrolisthes eriomerus , had ovigerous individuals 

 to August. Pugettia producta were ovigerous July 

 to November. 



Ovigerous crabs and pre- and posttest zoeae 

 were held in aquaria receiving running seawater- 

 of temperatures ranging from 8.2° to 23.5°C (Table 

 1); salinity ranged from 24.1 to 28.3%o; and 

 dissolved oxygen ranged from 5.6 to 9.0 ppm. 

 Laboratory water was sometimes 3°C higher than 

 ambient temperatures at the surface in the 

 afternoon on sunny days in July and August 

 because of heating of the water supply pipe. Other 



TABLE 1. — Temperature of Mukilteo, Wash., laboratory sea- 

 water summarized by 10-day periods in 1972. 



than this, the ambient water temperatures of the 

 Mukilteo area were similar to that expected of 

 central Puget Sound locations (Wennekens 1959). 



Test facilities consisted of floating holding 

 boxes for test groups of zoeae and 5 Jiter battery 

 jars for maintaining water baths of a controlled 

 temperature. Holding boxes were 2.5 cm 3 , with 

 two screened sides having 0.110-mm apertures, 

 attached to Styrofoam 5 for floatation. Battery jars 

 received 3 liters of seawater immediately before 

 testing. Temperatures were maintained within 

 ±0.5°C of the test temperatures during experi- 

 ments. Continuous aeration insured mixing and 

 oxygenation. 



Zoeae generally hatched within a week after 

 their parents were collected, but some parents 

 were held a month before hatching occurred. 

 When the zoeae hatched (hatching of all ova of a 

 parent occurred within about 12 h), 10 were 

 counted into each of the holding boxes within 24 h 

 of hatching and remained there, unfed, to the 

 termination of an experiment. Zoeae used as 

 controls were held at the temperature of labora- 

 tory water, and others were given two types of 

 thermal tests. 



To simulate passage through heat exchangers, 

 holding boxes containing 10 zoeae were removed 

 from water of ambient temperature and placed 

 directly into battery jars having water of an 

 elevated temperature ranging from 24° to 38°C by 

 2°C increments (Table 2). The zoeae remained at 

 the elevated temperature for 20 min and were 

 then placed into water of ambient temperature. 

 Actual temperature change within the holding 

 boxes was delayed. On the average, the increase 

 from ambient to midway to the test level occurred 

 in 5 s. Temperatures were within 1°C of the test 

 level in 2 min. Decreases from test temperatures 

 to ambient occurred in about IV2 min. Activity of 

 zoeae was noted before, during, and after testing. 



To simulate conditions encountered in thermal 

 plumes, zoeae in holding boxes were placed in 

 water of ambient temperature in the battery jar. 

 The temperature of the water was then elevated to 

 a test temperature ranging from 24° to 36°C by 2°C 

 increments (Table 2) over a 30-min period. 

 Specific groups of zoeae were held at specific test 

 temperatures for durations of 1, 2, or 4 h. After 

 this, the temperature was gradually decreased to 

 ambient level over a 20-min period, and the 



5 Reference to trade name does not imply endorsement by 

 the National Marine Fisheries Service, NOAA. 



556 



