FISHERY BULLETIN; VOL. 72. NO. 2 



either orbit of ERTS-1. Orbits instead occurred 

 on the 29th (eastern portion) and 30th (western 

 portion) of September 1972, representing 24- 

 and 48-h differences, respectively. 



The 25 research boats generally occupied 95 

 stations in the Mississippi Sound and 46 stations 

 in the offshore portion of the study area. These 

 stations were spaced to provide a sampling density 

 of about one station per 29 km^ in the Sound and 

 one station per 60 km^ in the offshore waters. 

 Parameters measured included surface tempera- 

 ture, salinity, chlorophyll a, currents, sea state, 

 water color, water depth, and secchi disc trans- 

 parency. Surface water temperature, salinity, 

 and chlorophyll a measurements were obtained 

 from bucket samples. Temperature was deter- 

 mined immediately in the bucket, and poly- 

 propylene bottles were used to store samples for 

 chlorophyll a and salinity measurements in the 

 laboratory. Color was estimated with a Forel- 

 Ule color comparator (Hutchinson, 1957), and 

 current speed and direction were measured by 

 timed drifts of neutrally buoyant floats. 



Fisheries Data 



Aerial photography provided most of the 

 fisheries distribution and abundance information 

 augmented periodically with nighttime, low- 

 light-level television sensor missions and com- 

 mercial fish-spotter pilot reports. Menhaden are 

 particularly susceptible to aerial sensing tech- 

 niques because of their characteristic surface or 

 near-surface schooling behavior. Discussions on 

 aerial photography and low-light-level tele- 

 vision sensing of fish schools have been pub- 

 lished by Bullis (1967), Benigno (1970), Drennan 

 (1969), and Roithmayr and Wittman (1972). 



Photographic fish sensing missions were flown 

 to provide 95% coverage of the study area at a 

 scale of 1:16,200. The camera used was a Zeiss 

 RMK-1523 mapping camera with a 15.24-cm 

 focal length lens and 22.86-cm film format. The 

 camera was supplied with GAF-1000 blue insen- 

 sitive (2575) film, selected for its speed and re- 

 ported ability to penetrate the hydrosphere (Vary, 

 1969). Photographic missions were divided into 

 morning and afternoon flights corresponding to 

 sun angles of 15 to 50 degrees, with morning 

 flights covering the Mississippi Sound and 

 afternoon flights covering the offshore section of 

 the study area. A Houston-Feerless film viewer. 



providing magnifications of 3 x to 33 x , was used 

 to aid in the search of processed film for imaged 

 menhaden schools. Fish school locations were 

 recorded according to latitude and longitude with 

 an accuracy of ±0.4 km. Menhaden schools could 

 be subjectively differentiated from other schooling 

 species in the study area on the basis of size, shape, 

 and color. 



Commercial Fishing Data 



Fishery and oceanographic parameter measure- 

 ments were obtained June through September 

 1972 from one to three commercial fishing vessels. 

 These measurements were taken at the time 

 and location of capture or attempted capture of 

 a menhaden school. Data collected included sur- 

 face water temperature and salinity, secchi 

 disc transparency, Forel-Ule color, number of 

 fish captured (visual estimate), date, time, and 

 location. Usually, these observations were 

 made the first three days of each fishing week 

 (Monday through Saturday) except during periods 

 when an ERTS-1 overpass or main day occurred, 

 in which case the sampling period was extended 

 over the entire fishing week. 



DATA ANALYSIS AND 

 INTERPRETATION 



General Analytical Rationale 

 and Data Limitations 



Because the overall success of the experiment 

 depended upon finding relationships between 

 menhaden distribution and abundance and 

 oceanographic parameters, the logical point of 

 departure was with these relationships. Thus, 

 impetus initially was given to finding relation- 

 ships between fish distribution and abundance 

 and selected oceanographic parameters, and then 

 to determine if parameters which had fisheries 

 meaning could be measured remotely with suf- 

 ficient accuracy for precise correlation analysis. 

 The last step in the analytical rationale was to 

 determine what, if any, uses these relationships 

 might have for commercial fishing and resource 

 management. 



The principal data limitation placed on early 

 analyses was a general lack of remotely acquired 

 synoptic oceanographic parameter measure- 

 ments. The conversion of remotely acquired 



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