Ja. Koslow et al., THE MID-SLOPE DEMERSAL FISH COMMUNITY OFF SOUTHEASTERN AUSTRALIA, Deep-sea research. Part 1. Oceanographic research papers, 41(1), 1994, pp. 113-141
The mid-slope (800-1200 m) demersal fish community off southeastern Au
stralia was sampled at 376 random, depth-stratified trawl stations. Th
e mean density of demersal species was 4.82 g m-2. Thirty-seven famili
es and 111 species of demersal fish were represented in the catch. The
density of mid-slope fishes off southeastern Australia was comparable
to that observed in the Northern Hemisphere. However, landings and ac
oustic and egg surveys of orange roughy (Hoplostethus atlanticus) indi
cate that densities of that species alone are an order of magnitude hi
gher than the total fish density indicated by trawl surveys. Water-col
umn productivity over the mid-slope region appears insufficient to sup
port the higher range of density estimates, implying a significant flu
x of energy into the region either from offshore or downslope. The dom
inant mid-slope demersal fishes appear to comprise an identifiable com
munity within a biogeographic province that extends at least from the
Great Australian Bight to the Chatham Rise (New Zealand), a distance o
f approximately 5000 km. Distinct assemblages of demersal fish were fo
und at upper (500 m) and mid-slope (800-1200 m) depths off southeast A
ustralia. The mid-slope community could be sub-divided into assemblage
s by depth (shallow. intermediate and deep) and area (east and west Ta
smania), which were statistically robust although with considerable ov
erlap of species composition. There was no overlap in species composit
ion of the southeast Australian mid-slope demersal fish community with
fish communities at similar latitudes and depths in the North Pacific
, but there were affinities with those in the North Atlantic. These bi
ogeographic patterns, which appear consistent with oceanic circulation
at intermediate depths, provide strong evidence that negates the rece
nt hypothesis that deepwater fish communities cannot be defined over b
road areas and are only random assemblages (HAEDRICH and MERRETT, 1990
, Progress in Oceanography, 24, 239-250).