11-49 



may be utilized by predators, particularly the bluefish (Bigelow and 

 Schroeder, 1953) . Menhaden are exploited extensively by commercial 

 fleets for fish oil, meal and by-products (ASMFC, 1965) . 



Gill nets have accounted for most of the adult catch, which 

 has fluctuated from year to year between a mean of 2.6 and 15.7 fish per 

 net haul (Figure 11-16) . Juveniles have been collected in more sub- 

 stantial numbers by beach seine and otter trawl (Figure 11-17) , espec- 

 ially in 1971 and 1972 (up to 6800 fish per seine, and 390 fish per 

 trawl). These large catches were taken in August, September, and 

 October and consisted of young-of-the-year (Figures 11-16, 11-17) . 

 Along with the ichthyoplankton record, these data indicate a peak in 

 utilization of New Haven Harbor as a menhaden nursery in 1972. 



Menhaden are often the subject of massive "fish kills" (West- 

 man and Nigrelli, 1955) . Several recent kills of adults and juveniles 

 have been observed to be associated with the thermal plumes produced by 

 discharging heated water from power plants (Young, 1974) , particularly 

 when discharge is into a canal or other restricted area. Various 

 explanations for the deaths have been suggested: one plausible under- 

 lying factor is suffocation brought about by the crowding; Oviatt, Gall 

 and Nixon (1973) noted an approximate 12% reduction of dissolved oxygen 

 concentration within menhaden schools ; other possible causes include 

 heat shock, cold shock, gas embolism, toxic effects of biocides and 

 pollutants (Young, 1974) . To maintain adequate oxygen supply to the 

 gills (which also serve as the filtering apparatus for obtaining micro- 

 planktonic food) menhaden must constantly remain in rapid motion. Even 

 20 minutes of confinement in a 20-gal aquarium tank is lethal for juve- 

 nile fish (3 to 7 cm long) . On the other hand, other juveniles can be 

 kept alive for several days in a flume (author's observation). 



Available records indicate that New Haven Harbor has been a 

 site of large fish kills involving menhaden, both before and after New 

 Haven Harbor Station began operation. Records maintained by the Conn- 



(Text continued on page 11-53) 



