NOAA PROFESSIONAL PAPER 11 

 Table 13-11. — Finfish avoidance of anoxic water mass and subsequent repopulalion of an area as demonstrated bx trawl catches. August 6-/7, 7976 



Location 39°30'N 74°08' W 38°30'N 74°0r W 39°30'N 73°55' W 



Station number 23 29 90 24 30 91 ~25 31 92 



Depth (m) 17 18 20 26 23 25 25 26 26 



Bottom temperature (° C) 11.1 17.4 16.3 10.8 15.0 13.4 11.1 17.4 11.6 



Bottom dissolved oxygen (ml/I) 0.00" 3.36 0.28 0.00 2.91 0.01 0.00 3.36 0.61 



Date: Month August'' August August 



^^-^ 9 10 16 9 11 16 9 11 16 



Common name: Scientific name: 



Smooth dogfish Mustelus cams X 



Striped anchovy Anchoa hepsetus X 



Silver hake Merluccius bilinearis X 



Spotted hake Urophycis cliuss X X 



Lined seahorse Hippocampus erectus X 



Black sea bass Centroprislis striata X 



Scup Stenolomus chrysops X 



Weakfish Cynoscion regalis X 



American sand lance Ammodytes americanus X 



Butterfish Peprilus truicanthus X X XX 



Northern searobin Prionotus carolinus XX X 



Summer flounder Paralichthys dentatus X 



Windowpane Scophthalmus aquosus X X 



Gulf Stream flounder Cithanchthys arclifrons X 



Longfin squid Loligo pealei X X 



' Indicates oxygen level below detection limit of method used. 



'' August 9, day before hurricane Belle; August 11, day after hurricane Belle; August 16. approximately 1 week after hurricane Belle. 



Somero 1971). For example, during winter conditions 

 European carp (Cyprinus carpio) often become "ice- 

 locked" in small ponds that gradually become anaerobic 

 and remain oxygen free for 2 to 3 months until the spring 

 thaw. Coulter (1967) identified 10 species of benthic fishes 

 that appear to live in, or tolerate, extremely low D.O. 

 concentrations for extended periods in Lake Tanganyika. 

 The number of fish species with anaerobic mechanisms is 

 unknown. We would expect to find them in bodies of 

 water with large fluctuations in D.O., such as some ponds 

 or lakes, or in essentially stagnant waters, such as some 

 fiords, or the abyssal areas of the Black Sea. rather than 

 in the relatively shallow waters of the continental shelf off 

 New Jersey (Davis 1975). Hall ( 1929) found that the oyster 

 toadfish (which prefers estuaries) "often lives in stagnant 

 water and readily survives 24 hours in oxygen-free water." 

 Anaerobic metabolism, if possessed, seems to be used 

 only when respiration is not feasible. 



Avoidance Behavior 



What our data do show is that instead of dying, finfish 

 in most cases were able to avoid the low D.O. area. This 

 avoidance and subsequent repopulation is well demon- 

 strated by the results of three stations that were sampled 

 three times (table 13-11) during the August RV Atlantic 

 Twin cruise. These three stations were first occupied the 

 day before hurricane Belle passed (August 10, 1976). The 

 second sampling was on the day after the hurricane passed. 

 The last sampling was about 1 week later. 



The first time these stations were sampled, the bottom 

 D.O. levels were so low that they were below the detection 

 limits of the method used. Of the species captured, only 

 the American sand lance (Ammodytes americanus) is 

 usually found closely associated with the bottom; the other 

 species are able to thrive in, and probably were captured 

 well up in, the water column above the anoxic water. The 

 sand lance was probably taken in the upper layers, because 

 the combination of anoxia and hydrogen sulfide poisoning 

 would preclude life lower down. 



Immediately after the passage of hurricane Belle, sev- 

 eral demersal finfish species had repopulated the previ- 

 ously vacated area. This was a direct result of the extensive 

 mixing that had brought the oxygen levels to over 2.8 ml/ 

 1 at all three stations. However, offshore waters of depths 

 greater than 33 m were unaffected by the storm and bot- 

 tom D.O. remained low. Station 32 (NMFS 1977), which 

 was 9.3 km farther offshore than station 31 (NMFS 1977), 

 had a D.O. of 0.26 ml/1. No finfish were taken at this 

 station. Bottom D.O. east of this station was not detect- 

 able. 



About 1 week later, these stations were revisited and 

 the anoxic water mass was again shifting toward the coast- 

 line. Two stations had less than 0.4 ml O./l, and no finfish 

 were taken. At station 92 the D.O. was about 0.6 ml/1 O,, 

 and seven species of demersal finfish were taken, probably 

 from either a lens or a tongue of water with a higher 

 oxygen level. In either case, obviously these fish actively 

 sought out or stayed in waters with higher oxygen con- 



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