THE PRODUCTION AND TROPHIC ECOLOGY OF SHALLOW-WATER FISH ASSEMBLAGES IN SOUTHERN AUSTRALIA .3. GENERAL RELATIONSHIPS BETWEEN SEDIMENTS, SEAGRASSES, INVERTEBRATES AND FISHES
Gj. Edgar et C. Shaw, THE PRODUCTION AND TROPHIC ECOLOGY OF SHALLOW-WATER FISH ASSEMBLAGES IN SOUTHERN AUSTRALIA .3. GENERAL RELATIONSHIPS BETWEEN SEDIMENTS, SEAGRASSES, INVERTEBRATES AND FISHES, Journal of experimental marine biology and ecology, 194(1), 1995, pp. 107-131
Fishes and benthic invertebrates were sampled in seagrass and unvegeta
ted habitats at 14 localities across southern Australia in order to de
termine any consistent relationships between animal production, fish c
onsumption and environmental parameters over a large spatial scale. Mo
st of the features identified in a related study at Western Port were
confirmed over the extended geographic range; however, an exception wa
s that the production of fishes in the smallest size-classes (i.e. <1
g wet weight) was not consistently greater in seagrass habitat than un
vegetated habitat. The more important characteristics of seagrass and
unvegetated habitat types identified in the extended study were (1) mo
re fish species were associated with seagrass habitat than unvegetated
habitat, (2) the majority of small-fish species in both habitat types
fed on crustaceans, with relatively few species capable of utilising
algae and virtually no species utilising seagrass, (3) the few species
that did ingest algae often occurred in high abundance, (4) the size
of prey eaten by fishes increased consistently with fish size, with pr
ey length averaging approximate to 6% of fish length, (5) abundant lar
ge fish species generally consumed smaller prey than rarer large fish
species at the same body size, (6) greater benthic invertebrate and de
mersal fish production occurred in seagrass habitat than in unvegetate
d habitat, (7) most of the production of crustaceans >1-mm sieve size
was ingested by fish predators while only a small proportion of non-cr
ustacean benthic production was consumed. Fish production was highly c
orrelated with crustacean production and seagrass biomass, and was neg
atively correlated with wave exposure (measured as fetch) across the r
ange of sites. The estimated production of crustaceans was highly corr
elated with the biomass of seagrass material and also with the proport
ion of particles <63 mu m in the sediments. The overall relationships
between macrofaunal production (M: mg . m(-2). day(-1)), macrocrustace
an production (C; mg . m(-2). day(-1)). demersal fish production (D; m
g . m(-2). day(-1)), fetch (F; km), seagrass biomass (L; g . m(-2)), p
roportion of particles <63 mu m (S;%) and temperature (T;degrees C) we
re: In M = 1.41 + 0.088 In (L + 1) + 0.38 In S + 0.89 In T. In C = -0.
93 + 0.27 in (L + 1) + 0.22 In S + 0.89 In T. In D = -1.23 - 0.62 In F
+ 0.36 In (L + 1) + 1.04 In T. These regression equations can be used
as models to predict the production of macrofauna, crustaceans and sm
all fishes at unexamined sites. When predictions were compared with es
timates of annual production at the eight sites previously examined in
Western Port, most predictions lay between 50 and 200% of measured va
lues. Additional work in Australia and overseas should allow these mod
els to be refined.