BATH and O'CONNOR: BIOLOGY OF WHITE PERCH IN HUDSON RIVER ESTUARY 



speed for trawling was about 3.4 km/h. Details of 

 the towing procedure are described in Rathetal. 

 (1979). 



The gill net was an experimental type with 

 four panels of varying mesh size. The net mea- 

 sured 30.4 m by 1.8 m and contained 7.6 m each of 

 12.7, 25.4, 38.1, and 76.2 mm stretch mesh mono- 

 filament line. It was hung from 9.5 mm braided, 

 polycore float line, with a bottom lead-coreline. 



All fish collected at each site were immediate- 

 ly labeled and preserved in 10% Formalin 8 and 

 returned to the laboratory for analysis. Each 

 fish was measured (standard length (SL)) to the 

 nearest millimeter, weighed to the nearest 0.1 g, 

 and the sex was determined. A subsample of 310 

 fish was measured for fork length (FL) and total 

 length (TL) to determine regression equations 

 for comparison of Hudson River white perch 



'Reference to trade names does not imply endorsement by 

 the National Marine Fisheries Service, NOAA. 



populations with data from other river systems. 

 Mature ovaries and testes were removed from 

 selected individuals, weighed, and preserved in 

 10% Formalin. The ovaries were later transfer- 

 red to (iilson's fluid for fecundity analysis! Ricker 

 1968). Stomachs were removed from randomly 

 selected fish and preserved in 10% Formalin for 

 later food analysis. Scales for age analysis were re- 

 moved from behind the left pectoral fin (Rounse- 

 fell and Everhart 1953), cleaned, pressed, and 

 sealed between glass microscope slides. The 

 scales were read within 6 mo of the collection 

 date. 



RESULTS 



Time of Annulus Formation 



Annulus formation began by the first week in 

 May and was completed in all age groups by the 

 end of July (Table 1). Younger fish (age groups 1 

 and 2) completed the annulus by the end of June. 



Table 1.— Percentage of aged white perch, Morone americana, with a new annulus and with a given number of 



circuli beyond the new annulus during a given period. 



Date 

 collected 



Age 

 (winters 

 of life) 



No. 

 spec 



Percent 

 with new 

 annulus 



Percent with noted no. of 

 circuli beyond new annulus 



1-2 



3-4 



5-6 



7-8 



>8 



601 



