Adult golden perch Macquaria ambigua were fed to satiety, starved for up to 210 days, or starved for 150 days then fed to satiety for 60 days to investigate the utilization of energy stores in response to food deprivation and re-feeding. Golden perch sequentially mobilize energy from hepatic tissue, extra-hepatic lipid, and finally muscle components in response to food deprivation. The relative size of the liver was significantly reduced by 30 days after the onset of food deprivation due to the simultaneous mobilization of lipid, protein and glycogen reserves. These stores were renewed rapidly within 30 days by satiety feeding. Mobilization of lipid stores in perivisceral fat bodies occurred between 30 and 60 days of food deprivation. These deposits were also renewed upon re-feeding, although not as rapidly as liver reserves. The glycogen content of the epaxial muscle was reduced by the 60th day of food deprivation but subsequently increased indicating the mobilization of other energy reserves. The concentration of muscle lipid decreased after 90 days of food deprivation. The only significant response in body composition observed in the fish fed to satiety throughout the study was an increase in the relative size of the perivisceral fat bodies. The results of this study suggest that golden perch are well adapted to cope with extended periods of food deprivation, storing energy as perivisceral fat when food is readily available and having a clearly sequential process for mobilizing energy when food is scarce which largely protects the integrity of the musculature. C) 1995 The Fisheries Society of the British Islo
The gastrointestinal tract of Girella tricuspidata, an herbivorous teleost, is differentiated into esophagus, stomach, pyloric caeca, intestine, and rectum. The mucosa of the esophagus consists almost entirely of elongated secretory cells, with an underlying submucosa and prominent circular and longitudinal muscle layers. The anterior part of the stomach contains a mucous surface epithelium and a network of tubular glands having only one type of glandular cell, to which secretion of both pepsinogen and HCl is attributed. The tubular glands are not present in the pyloric region. The gastric wall contains well developed circular muscle and submucosal layers. The pyloric caeca contain a mucosa containing two types of exocrine cells. The nature and function of secretions from these cells is discussed. The intestinal mucosa is differentiated into an anterior (ca. 30%) and a posterior section. The enterocytes of the anterior portion show evidence of lipid absorption, while those of the posterior intestine and rectum show considerable pinocytotic activity. The pyloric caeca, intestine, and rectum have a layer of submucosa and a thin layer of circular muscle. The presence of the prominent circular muscle in both the esophagus and the stomach is postulated to be advantageous to an herbivorous fish. However, other ultrastructural features of the gastrointestinal tract of the luderick are similar to those described in carnivorous fish and appear to show no specialization for herbivory.
An experiment was carried out to determine the effects of dietary ¢sh oil replacement at an optimal level on the growth and carcass proximate composition of juvenile barramundi or sea bass (Lates calcarifer). Ten ¢sh feeds were formulated to contain iso-ingredients with theoretically identical dietary lipid levels but with di¡erent sources of lipids (¢sh oil, soybean oil, canola oil and linseed oil) replacing dietary ¢sh oil. Three hundred ¢sh were equally divided into 30 70-L plastic tanks (three replicate tanks for each treatment). Fish were fed with experimental diets for 40 days within closed recirculating freshwater systems (70 L h À 1 , 28 1C and 12L:12D). Growth, speci¢c growth rate, food conversion ratio (FCR) and carcass proximate composition were determined. Dietary lipids signi¢cantly a¡ected (Po0.05) the growth of the ¢sh. Good growth and low FCR were observed in all treatments. Therefore, ¢sh oils can be partially replaced by vegetable oils to reduce the feed cost. There were no signi¢cant di¡erences (P40.05) in lipid, moisture and protein content in ¢sh carcasses among the group. However, juvenile barramundi showed increasing lipid and moisture content in muscle, whereas decreasing protein content when compared to the initial ¢sh.
The gonadal development, reproductive cycle and growth of Macquarie perch,
Macquaria australasica Cuvier, in Lake Dartmouth and
selected tributaries of the Murray–Darling River Basin in south-eastern
Australia were evaluated. Gonadosomatic index (GSI) and histological analysis
were used to determine gonadal development and age and size at first maturity
in the resident Lake Dartmouth population. GSI analysis was also used to
determine age and size of Macquarie perch at first maturity in the inflowing
Mitta Mitta River and other riverine populations within the Goulburn River
catchment. Males appeared slightly smaller at first spawning than females at
all sites; both sexes were fully mature at four years of age. Differences in
size at first maturity were found between the lake and river populations; both
males and females of river populations tended to mature at a much smaller size
than the fish resident in the lake. Spawning occurred around November. Ovarian
and testicular development in this species follows a pattern similar to that
of other native Australian percichthyids. The implications for management of
recreational fisheries based on minimum size regulations is discussed in
relation to site-specific differences in growth rates and size of first
maturity of fish.
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