HOUDE: ABUNDANCE AND POTENTIAL YIELD OE ROUND HERRING 



TABLE 1 . — Summarized data on cruises to the eastern Gulf of Mexico, 197 1 -74, to estimate abundance of round herring eggs and larvae. 

 (GE = RV Gerda, 8C = RV Dan Braman, TI = RV Tursiops, 8B = RV Bellows, IS = RV Columbus Iselin, CL = RV Calcnus.) 



'Positive station is a station at which round herring eggs were collected. 



2 Positive station is a station at which round herring larvae were collected. 



3 An ICITA, 1-m plankton net was used on this cruise. On all other cruises a 61 -cm Bongo net was used. 



4 No stations in offshore areas were sampled, accounting for the failure to collect round herring eggs or larvae on this i 



TABLE 2. — Summary of plankton tow characteristics for 17 ichthyoplankton cruises to the eastern Gulf of Mexico. The 

 61-cm Bongo net sampler was used on all cruises except GE 7101 in which a 1-m ICITA net was used. 



GE7101 



8C7113& TI 7114 



GE 7117 



8C 7120 & TI 7121 



8B7132&TI 7131 



GE 7202 & 8B 7201 



GE 7208 



GE 7210 



IS 7205 



IS 7209 



IS 7303 



IS 7308 



IS 731 1 



IS 7313 



IS 7320 



CL 7405 



CL7412 



20 



358 



335 <55 m 

 deep 



124 >55 m 

 deep 



675.25 



160.17 



104.39 



231 .93 



30 29 



7.27 



0.92 



11.80 



1.44 



1.17 



1.18 



0.03 



0.01 



0.01 



49.69 



3.60 



11.04 



2.37 



11.58 



0.11 



0.57 



0.07 



wire release at 50 m/min to desired depth and 

 retrieval at 20 m/min. In later cruises, two types of 

 tow were used, a shallow-water tow at stations less 

 than 55 m deep and the usual 50 m/min release-20 

 m/min retrieval tow at deeper stations (Table 2). 

 The shallow-water tow was of 5-min duration; it 

 consisted of 1 min for wire release and 4 min for 

 wire retrieval. The objective at shallow stations 

 was to filter 100 m 3 of water. This objective was 

 met, but the volume of water filtered per unit of 

 depth fished by the net was increased significantly 

 at the shallow stations relative to deeper stations 



(Table 2). This discrepancy in type of tow was 

 considered to be more desirable than the alterna- 

 tive situation, which existed in 1971, when as lit- 

 tle as 25 m 3 of water were filtered at some of the 

 shallowest stations. Tows at stations deeper than 

 55 m filtered between 100 and 400 m 3 . 



A stopwatch was used to monitor each tow and 

 the wire angle was measured at the end of each 

 minute of a tow. A time-depth recorder gave a 

 record of tow characteristics. Volume filtered was 

 determined from a flowmeter in the mouth of the 

 505-yu.m mesh net. 



63 



