FISHERY BULLETIN: VOL. 78, NO. 3 



erance of S. empusa is presented and a compari- 

 son of the laboratory result with the observed dis- 

 tributions is made. 



METHODS 



Research Applied to 

 National Needs (RANN) Survey 



The sampling area extended from lat. 37°40' N, 

 just north of the Rappahannock River, to the bay 

 mouth, an area covering 1,300 km of the lower 

 Chesapeake Bay (Figure 1). The survey area was 

 divided into eight subareas designated A through 

 H. A, D, and G were situated in the western por- 

 tion and B, F, and H in the eastern section of the 

 bay. These divisions were based on salinity differ- 

 ences in the bay, while areas C and E were sepa- 

 rated because they represented channel areas. 



Figure l.— Subareas (A-H) of RANN survey, August 1971 to 

 July 1973, in lower Chesapeake Bay, Va. 



The study area, consisting of 688 stations set 1.8 

 km apart, was sampled from August 1971 to July 

 1973. Three to five stations were randomly 

 selected from each subarea to be sampled each 

 month. 



The plankton samples collected during the 

 RANN survey were taken with a bongo sampler, 

 having a mouth diameter of 18.7 cm (8 in) and 

 equipped with 202 /xm mesh nets. Stepped oblique 

 tows were taken for varying lengths of time at 

 each station, depending on station depth. A sub- 

 mersible pump was used at depth intervals of 2 m 

 to gather hydrographic data. The temperature and 

 salinities taken at each interval from each station 

 were then averaged. All tows were taken during 

 daylight. The stomatopod larvae were sorted from 

 the general catch by the Virginia Institute of 

 Marine Science staff and staged by the author. 



Cape Henry Survey 



Using the Old Dominion University RV Lin- 

 wood Holton , larval specimens of S. empusa were 

 collected weekly at Cape Henry where a popula- 

 tion of adults exists. By using a V2 m plankton net 

 (153 /xm mesh), 10 min stepped oblique tows were 

 accomplished as the ship circled the collection site 

 at idle speed. The volume of water filtered through 

 the net was calculated from the duration of the tow 

 and the area of the net because the flowmeters 

 employed yielded wildly erratic readings. The 

 volume of water filtered for a 10-min tow was cal- 

 culated to be 47.6 m^. Surface and bottom water 

 temperatures and salinities were recorded for 

 each tow, using an inductive salinometer with a 

 45.7 m cable. 



Upon collection each plankton sample was 

 placed in a 1.9 1 (y2-gal) jar and filled with seawa- 

 ter. Samples containing large amounts of biomass 

 were split into two such jars to facilitate the survi- 

 val of the stomatopod larvae until they could be 

 separated from the sample. As many larvae as 

 possible were extracted from the samples aboard 

 the ship and the task was completed in the 

 laboratory. These larvae were placed in 1.9 1 jars 

 filled with seawater and were grouped according 

 to size so that cannibalism would be minimal. The 

 jars were aerated until the samples reached the 

 laboratory, whereupon the larvae were placed in 

 compartmentalized plastic trays, one per com- 

 partment. Each compartment measured 4.5 x 5 x 

 4 cm. Medium used for rearing the larvae was 



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