JLjNE: ATLANTIC MENHADEN GROUPINGS 



summer schools also has important implications 

 in regard to the yield that may be expected at 

 different levels of fishing and to the well-being 

 of the population. Since the fish are differen- 

 tially distributed by length, with smaller fish oc- 

 curring in the South Atlantic and Chesapeake 

 Bay Areas during the greater part of the year, 

 a disproportionate increase in the fraction of the 

 population taken in these areas would be ex- 

 pected to result in a substantial reduction in the 

 stock of larger fish available in the Middle and 

 North Atlantic Areas. Putting it another way, 

 a given unit of effort in the two southern areas 

 imposes a higher fishing mortality rate. More- 

 over, immoderate fishing on the recruit stock 

 in the two southern areas may also be expected 

 to result in a drastic reduction in the size of the 

 spawning stock. Thus, a stock-recruitment 

 model that incorporates information on school 

 size, number, and composition is less likely to 

 fall short of realistic estimates of the levels of 

 fishing commensurate with a desirable popula- 

 tion structure and the optimum catches that may 

 be expected therefrom. 



If the role of schooling in the dynamics of the 

 Atlantic menhaden population is to be under- 

 stood, the research must be based on broader 

 considerations than the classical methods of 

 stock assessment. Limiting interpretation of 

 changes in the population to simple relationships 

 between fishing effort and catch is to ignore the 

 dynamic aspects of fish schooling implied 

 throughout this paper. Because of the selective 

 nature of purse-seine fishing, fishermen's log- 

 books and catch records can only furnish indirect 

 evidence of changes in the behavior and habits 

 of the fish due to fishing. Furthermore, in- 

 creased efficiency in the methods of menhaden 

 fishing, coupled with technical improvements in 

 fishing gear and vessels, has greatly altered long- 

 term measures of effective fishing effort with the 

 probable result that fishing mortality tends to 

 be underestimated and changes in schooling of 

 the fish minimized or perhaps obscured. Thus, 

 there is a primary need for direct measures, 

 independent of fishing, of school biomass and 

 number and distribution of schools in the sea, 

 including correlative measures of the fall school- 

 aggregations off Long Island and North Caro- 



lina. With menhaden, direct aerial observations 

 or photography and remote sensing are practi- 

 cable (see, e.g., Roithmayr, 1970). Recent 

 advances in underwater acoustical techniques 

 (see, e.g., McClendon, 1968; Smith, 1970; Love, 

 1971) oflFer a supplementary means of identi- 

 fying and quantitatively assessing the size and 

 composition of menhaden schools. 



Finally, development of a fully analytical ap- 

 proach to the role of schooling in the study of 

 the dynamics of the Atlantic menhaden popu- 

 lation requires a broad spectrum of information 

 on the behavior of the fish in relation to envi- 

 ronmental factors and other fishes. Briefly, what 

 is needed is a more or less continuous picture of 

 what the schools are doing. Included here are 

 (1) the nature of short-term, i.e., day to day, 

 changes in the behavior, structure, and distri- 

 bution of summer schools in response to changes 

 in light, salinity, temperature, currents, and food 

 conditions, (2) the behavior of schools in isola- 

 tion and in association with other fishes, (3) the 

 primary mechanisms involved in the formation 

 of school-aggregations and the seasonal migra- 

 tions, and (4) the winter habits and wherea- 

 bouts of the fish. There, for example, are no 

 published data from which it is possible to esti- 

 mate the swimming speed or endurance of which 

 a school is capable in escaping a predator or a 

 net. Much information can be provided from 

 direct observations on the fish in free-swimming 

 schools under a variety of life conditions. Air- 

 craft are routinely employed in locating and di- 

 recting fishing operations (Squire, 1961; June, 

 1963), yet little use has been made in menhaden 

 research of either the information compiled by 

 individual fish spotters or the facilities offered 

 by the aircraft fleet. In practice this might 

 simply require the recording of aerial observa- 

 tions during fishing operations and special re- 

 connaissance flights as a means of assessing 

 changes in the distribution and size of schools or 

 school-aggregations during the fishing season, 

 or mapping the migrations of this fish. Ancil- 

 lary data on the behavior and physiology of the 

 fish may be generated from experimental stud- 

 ies in aquaria, artificial ponds, and temporary 

 enclosures in the sea. Any single approach to 

 the study of schooling of Atlantic menhaden has 



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