FISHERY BULLETIN: VOL. 76, NO. 2 



3-yr-old fish which are making their first annual 

 migration from their Chesapeake Bay nursery 

 areas to the northern summer feeding ground 

 (Austin and Hickey see footnote 4). The concen- 

 trated study of one age-group of fish permits 

 monitoring of the cohorts for successive years 

 starting with first departure from their home 

 grounds and, thereby, permits a description of dif- 

 ferences or variations in migration and abundance 

 on an annual basis, as well as an accurate evalua- 

 tion of year class mortality in successive years. 



METHODS AND MATERIALS 



Prerecruit striped bass were randomly removed 

 from the catches of commercial haul seine and 

 pound net fishermen in the waters of East 

 Hampton on the southeastern end of Long Island, 

 N.Y. (Figure 1). Samples were collected during 

 May and June 1972 and April-June 1974, thus the 

 age II fish were of the 1970 and 1972 year classes, 

 respectively. Fork lengths were measured in the 

 field to the nearest millimeter and scale samples 

 were removed for age determination. The fish 

 were then tagged (Floy*^ FD-69B anchor tags) and 

 released. The initial purpose of the study was 

 tagging of prerecruit fish to monitor the seasonal 

 migration and mortality of cohorts as they reached 

 legal size in the different states. The feasibility 

 study was focused on the 1970 and 1972 year 

 classes. Large differences in the modal size of the 

 fish in their third year (11 + ) existed between the 

 two year classes ( Figure 2 ) . The smaller sized 1970 

 year class of fish were from the most abundant 

 Chesapeake Bay year class on record (Schaefer 

 1972). Examination of the literature shows that 

 the length of cohorts may be inversely propor- 

 tional to the abundance or density of the fish (Ste- 

 vens 1977; Texas Instruments'' ), suggesting to us 

 that the length of the striped bass, when they first 

 appear in New York waters, could be an indicator 

 of year class strength and subsequently a means of 

 predicting stock abundance in local waters. Con- 

 sequently the focus of the study was redirected 

 towards examination of these differences. 



Schafer (1968, 1972) stated that most commer- 

 cially harvested striped bass in New York are of 

 four age-classes, III- VI. Based on this, Schaefer 



^Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



■'Texas In.struments, Inc. 1975. First annual report for the 

 multiplant impact study of the Hudson River estuary. Unpubl. 

 rep., vol. 1, p. VIII-8-VIII-12. Texas Instruments, Inc., Dallas, 

 Tex. 



r-l 



YC 1970 

 (in 1972) 



I 



YC 1972 

 (in 1974) 



I I 

 i_J 



350 

 FORK LENGTH IN MILLIMETERS 



Figure 2. — Length-frequency distribution of age II striped bass 

 captured by commercial fishing gear near eastern Long Island, 

 N.Y., during 1972 and 1974. 



(1972) related the New York harvest to a 4-yr 

 mean brood production (year class strength; ex- 

 pressed as annual mean number of juveniles per 

 standard seine haul in Chesapeake Bay, Md.) 3 to 

 6 yr prior to the harvest. He concluded that ap- 

 proximately 70% of the variability in annual New 

 York landings could be explained by annual fluc- 

 tuations in year class strength in Maryland wa- 

 ters of Chesapeake Bay. 



We hypothesized that the growth rate of striped 

 bass, and, therefore, the body length at the end of 

 the 2-yr residence time in the Chesapeake Bay 

 nursery grounds, is a density dependent function 

 with the length inversely proportional to the year 

 class abundance (number offish). This hypothesis 

 was tested via a correlation analysis using modal 

 lengths at age 11+ (our data combined with pub- 

 lished data of Alperin 1966 and Schaefer 1968) 

 and year class abundance indices supplied by the 

 Maryland Department of Natural Resources. The 

 analyses were performed using a Hewlett- 

 Packard Model 9100B programmable calculator 

 with an X-Y plotter, which provided both a regres- 

 sion line and a correlation analysis and coefficient. 



The relationship resulting from the above 

 analysis suggested that the density dependent 

 hypothesis is true. Since Schaefer ( 1972) described 

 a relationship between the annual New York har- 

 vest (reported commercial landings) of striped 

 bass and the Chesapeake Bay year class abun- 

 dance, and since we have described a probable 

 relationship between year class abundance and 

 modal length at age 11+ in New York waters, it 

 seemed reasonable to test the correlation between 



468 



