CHAPTER 13 



several kilometers away from shore; thus, the usual path- 

 way for these fish remained open almost all of the time. 

 This is supported by small-sized fish that had been tagged 

 off New Jersey and captured off New York City. It is also 

 supported by fishing reports of normal catches of this size 

 fish from along the south shore and eastern end of Long 

 Island and along the shores of Rhode Island and southern 

 New England. 



The offshore contingent of bluefish seemingly were not 

 affected by the anoxic water and proceeded on their north- 

 ward migration uninhibited. The usual pathway for these 

 2.7 to 6.8 kg fish was apparently seaward of the farthest 

 extent of the anoxic water. Figure 4 illustrates the bluefish 

 migratory pattern that emerged as a result of the existence 

 of the anoxic water mass. 



Although the fish were avoiding the anoxic water mass, 

 on several occasions an undetermined number of fish were 

 trapped in the low D.O. mass near beaches. This occurred 

 in late July between Manasquan and Beach Haven, N.J., 

 when persistent westerly winds apparently blew the oxy- 

 genated surface waters offshore, causing an inshore move- 

 ment or upwelling of the anoxic bottom water. The trap- 

 ped fish were observed to be gasping at the surface and 

 behaving lethargically. Belding (1924) and Shepard (1955) 

 both found this type of behavior to be symptomatic of 

 depressed D.O. conditions. Species reportedly involved 

 were striped bass (Morone saxalilis), bluefish, weakfish 

 (Cynoscion regalis), windowpane (Scophthalmus aquo- 

 sus), summer flounder, and northern searobin (Prionotiis 

 carolinus). It was impossible to obtain an accurate esti- 

 mate of mortalities, because the gulls were very active; 

 some dead fish were observed on the beach. 



Reproductive Success 



In addition to supporting a diverse community of adult 

 fishes, shelf waters between Sandy Hook and Cape May 

 serve as spawning grounds for many of our most important 

 commercial and recreational fishes, and nursery grounds 

 for their young stages. Both eggs and larvae can be found 

 year-round, but most spawning takes place in spring, sum- 

 mer, and autumn. Although a few species spawn through- 

 out the year, most do so over a period of a few months 

 and, for most, spawning peaks during a period of weeks. 

 Successful spawning depends partly on an unknown com- 

 bination of environmental requirements that differ with 

 species and include such things as temperature, water 

 quality, and available food. The eggs and small larvae are 

 the most vulnerable life stage and therefore the most sen- 

 sitive to environmental changes (Voyer and Hennekey 

 1972). 



Alderdice et al. (1958) and Voyer and Hennekey (1972) 

 have studied the direct effects of low D.O. levels on em- 

 bryonic stages. Both studies concluded that depressed 

 D.O. retards the development of the embryo and delays 

 hatching. The effects of limited exposure can be reversed. 



but prolonged exposure results in irreversible damage 

 (and the production of monstrosities) or death. When eggs 

 in advanced developmental stages are exposed to de- 

 pressed D.O., hatching may be premature. 



Based on the information at hand, there seems no rea- 

 son to doubt that spawning was disrupted off New Jersey 

 during summer 1976. Adult fishes either avoided the large 

 area of anoxic water or perished. Because ichthyoplankton 

 samples were not collected during summer 1976, we do 

 not know what effect the anoxic water mass had on the 

 reproductive cycle of fishes that would have spawned off 

 New Jersey. We do have data from both historical and 

 recent cruises, indicating that a host of fishes spawn within 

 the area where the low D.O. prevailed in 1976 (table 

 13-3). We should point out that collecting gear and meth- 

 ods used in 1966 were different from those used in 1975 

 and 1976, and, given only the information in the table, 

 any attempt to equate catches from the two series of 

 cruises would produce invalid results. 



EFFECTS ON AMERICAN LOBSTER 



American lobster probably react to depressed oxygen 

 levels like finfish do. McLeese (1956) found that oxygen 

 uptake of small lobster is greater per unit weight than 

 large lobster; lobsters are able to acclimate to low-oxygen 

 concentrations; moulting lobsters are less resistant to low- 

 oxygen than hard-shell lobster; and the minimum D.O. 

 they can tolerate varies with temperature and salinity. As 

 an example of the way the minimum D.O. varies, at 15° C 

 with a salinity of 307oo the minimum DO. is 0.54 ml/I, 

 at 15° C with a salinity of 25°/oo the minimum is 0.63 ml/ 

 I, and at 5° C with a salinity of 30°/oo the minimum is 0. 19 

 ml/1. 



During the 1976 RV Atlantic Twin cruise the bottom 

 temperature in the anoxic area was 7° C to 12° C, while 

 the corresponding salinities were about 30 to 33°/oo 

 (Azarovitz, unpublished data). Applying McLeese's ob- 

 servations to these would seem to indicate that the min- 

 imum D.O. level that lobster could survive would be be- 

 tween 0.26 ml/1 and 0.43 ml/1. Much of the depressed D.O. 

 water mass had oxygen levels below these. If lobsters res- 

 ident to the areas affected did not leave, mortality would 

 result. 



Evidence is mixed on whether lobsters avoided or suc- 

 cumbed to anoxia. On June 27, 1976, divers observed that 

 lobsters that were apparently residents of certain wrecks 

 had climbed to the highest part of these wrecks. By July 

 4, 1976, these same lobsters were observed to be dead. 

 In mid-July other lobsters were observed to be lethargic 

 and lying outside their shelters, often with two or more 

 close to each other. This observation is significant when 

 we consider the aggressive behavior of lobsters. Late in 

 September, lobsters again inhabited these same wrecks. 

 The climbing behavior on the wrecks may indicate that 



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