Consumption, growth and evacuation in the Pacific cod, Gadus macrocephalus

Growth of Pacific cod was related to energy consumption (cal g⁻¹ day⁻¹) and was well described by linear equations. Maintenance ration was 11 and 12 cal g⁻¹ day⁻¹ at 4.5 and 6.5° C, respectively. Cod between 200 and 5000 g had similar growth rates when growth was expressed as a function of consumption (cal g⁻¹ day⁻¹). Laboratory consumption of food averaged 0.9 and 1.3% body weight per day at 4.5 and 6.5° C, respectively. At these temperatures growth was 0.34–0.38% body weight day⁻¹.
Maximum stomach volumes equated to approximately 4.7% of body weight with shrimp as prey. At this meal size Pacific cod did not feed the next day. A multiple meal evacuation experiment was used to verify the consumption estimates. A return-to-hunger estimate of the meal size evacuated was 1.5% body weight day⁻¹ at 6.5° C, similar to the 1.3% consumption estimate. For Pacific cod fed a single meal of 1% body weight the estimated instantaneous evacuation rate was 0.63 body weight day⁻¹ at 6.5° C. Meal size markedly affected the evacuation rate.
Measured consumption and growth rates are similar to those of Atlantic cod, Gadus morhua .     

Daily ration estimates for yellowfin sole, Limanda aspera (Pallas), based on laboratory consumption and growth

Several estimates of minimal energy requirements for yellowfin sole were made. Energy expenditures of 1.6, 4.1 and 8.3 cal g⁻¹ day⁻¹ were obtained from starvation weight loss, standard metabolism and maintenance ration procedures, respectively, at 6° C. The temperature effect on energy requirement was reflected in the Q ₁₀ values for starvation weight loss (2.0), standard metabolism (6.3) and maintenance ration (6.5).
Both energy intake and weight of food were linearly related to, and good predictors of, laboratory growth. These relationships were used to estimate the food and energy intake necessary for yellowfin sole to achieve a year's growth in the natural environment. Based on a caloric value of 2.0 kcal g⁻¹ of food (herring fillets), yellowfin would require 0.35 to 0.39% body weight day⁻¹ at 3° C to achieve the mean growth rate exhibited in the Bering Sea. To achieve Gulf of Alaska growth rates at 5 to 6° C, yellowfin would require 0.63% body weight day⁻¹. Based on a caloric value of 0.57 kcal g⁻¹ of food (chopped octopus), yellowfin would require 0.83% body weight per day to achieve the Gulf of Alaska growth rate (6° C). These requirements based on the calorific value of herring fillets, which are three to five times higher than previous estimates of daily ration in this species, are probably conservative estimates since many of their prey species have a lower energy content.     

Energy and ration requirements of juvenile Pacific halibut (Hippoglossus stenolepis) based on energy consumption and growth rates

Growth of captive juvenile Pacific halibut was linearly related to energy consumption (J g⁻¹ day⁻¹) at 4°C by the following equation: growth (% body weight (b.w.) day⁻¹)=0–007 (consumption J g⁻¹ day⁻¹)– 0.192; r² =0.81. Weight gain was independent of size for fish between 9 and 7000 g when growth was expressed as a function of consumption in J g⁻¹ day⁻¹. Maintenance ration determined in feeding–growth experiments averaged 27.4 J g⁻¹ day⁻¹ at 4–0°C. Small halibut ate significantly more food than large fish. Single meals following 2 day fasts averaged 4.1% b.w. for halibut under 100 g, 1.72% b.w. for 1.2 kg fish and 1.1% B.W. for 6.8 kg fish. Both large and small size categories of halibut tended to evacuate their meal in about 3 days even though small fish ate relatively larger meals. Minimum estimates for daily ration to achieve growth rates observed in the Gulf of Alaska were approximately 0.5 to 2.4% b.w. day⁻¹ depending on fish size and whether northern shrimp or yellowfin sole were their prey.     

Compensatory growth and reduced maturation in second sea winter farmed Atlantic salmon following starvation in February and March

Starvation of second sea winter farmed Atlantic salmon through February and March reduced body weight by 0.10% day⁻¹ or 6.0% during the starvation period, whereas fed fish increased body weight by 0.10 day⁻¹ or 5.9%. When fed again during 41 days in April and May, the starved group increased weight by 22.7% (0.55% day⁻¹) compared with a 11.4% (0.28% day⁻¹) gain in the unrestricted control. Ultrasound determination of sex and maturity in late May showed that the incidence of maturation was reduced by 48% among females and 32% among males in the starved group, compared with the unrestricted group.     

The effect of temperature and fish size on growth and feed efficiency ratio of juvenile spotted wolffish Anarhichas minor

The growth properties of juvenile spotted wolffish Anarhichas minor reared at 4, 6, 8 and 12° C, and a group reared under 'temperature steps', (T‐step) i.e . with temperature reduced successively from 12 to 9 and 6° C were investigated. Growth rate and feed efficiency ration was significantly influenced by temperature and fish size. Overall growth rate was highest at 6° C (0·68% day⁻¹) and lowest at 12° C (0·48% day⁻¹), while the 4 and 8° C, and the T‐step groups had similar overall growth rates, i.e . 0·59, 0·62 and 0·51% day⁻¹ respectively. Optimal temperature for growth ( T _{opt G} ) and feed efficiency ratio (T_{opt FCE}) decreased as fish size increased, indicating an ontogenetic reduction in T _{opt G} and T _{opt FCE}. The results suggest a T _{opt G} of juvenile spotted wolffish in the size range 135–380 g, dropping from 7·9° C for 130–135 g to 6·6° C for 360–380 g juveniles. The T _{opt FCE} dropped from 7·4° C for 120–150 g to 6·5° C for 300–380 g juveniles. A wider parabolic regression curve between growth, feed efficiency ratio and temperature as fish size increased, may indicate increased temperature tolerance with size. Individual growth rates varied greatly at all time periods within the experimental temperatures, but at the same time significant size rank correlations were maintained and this may indicate stable size hierarchies in juvenile spotted wolffish.     

Carbon, nitrogen and caloric content of eggs, larvae, and juveniles of the walleye pollock, Theragra chalcogramma

Measurements of dry weight (wt), carbon (C), nitrogen (N) and calories were made on walleye pollock eggs (0.24 mg, 35.3% C, 8.3% N, and 4.6 kcal g⁻¹ dry wt), larvae (0.16 g, 42.9% C, 11.1% N and 5.1 kcal g⁻¹ dry wt) and juveniles (22.4 g, 47.2% C, 9.0% N and 5.6 kcal g⁻¹ dry wt). For juvenile fish (9–360 g wet wt) the measured values were related to dry weight and Fulton's condition factor index (CFI) by regression models. The CFI was a better predictor of body composition than dry weight. As CFI improved from a minimum starvation level of 0.42 to a maximum of 1.16, body caloric content, percentage C, and the C/N ratio increased (kcal g⁻¹ dry wt = 4.4 CFI + 1.7, percentage carbon = 49.7 CFI^0.5, C/N ratio = 5.0 CFI + 0.9), while percentage N and percentage ash decreased (percentage N =−3.5 CFI + 12.1; percentage ash = 9.1 CFI^−1.4). The results of this study suggest that seasonal C, N and caloric content of young pollock can be estimated from measurements of Fulton's condition factor index.     

Protein, lipid and caloric contents of bluntnose minnow, Pimephales notatus Rafinesque, during growth at different temperatures

Changes in the relative proportions of protein, lipid, water and caloric contents of bluntnose minnow growing at various temperatures (15, 25, 30° C) were investigated by application of the allometry equation, y=ax^b . Fish grew significantly faster at 25° C (closest to optimum), more slowly at 30° C and most slowly at 15° C. Protein, as a percentage of body wet weight, tended to increase with fish size at all temperatures ( b > 1.000), whereas in juveniles (<0.7 g) it decreased ( b < 1.000). However, with the exception of the 15° C group, protein as a percentage of body dry weight, decreased in all groups ( b < 1.000). Temperature appeared to modify the body composition of bluntnose minnows, e.g. decreasing temperature led to significantly enhanced protein content during growth. Lipid (%) and caloric content (cal g⁻¹) increased with increasing fish weight ( b > 1). The slower growing fish (15°, 30° C) deposited significantly more lipid (and had higher caloric contents) than those growing most rapidly (at 25° C). Water content (%) decreased with increasing body weight in all groups. Despite intergroup growth rate differences, all groups showed evidence of a tendency to follow similar trends in b values for body constituents and caloric content (except for protein v. body dry weight for the 15° C group). This suggests a general conservativeness of body composition in bluntnose minnow. The correlations between body constituents, caloric content and body weight were high ( r ²>0.9) so that estimates of body composition can be obtained from body weight for all temperature groups.     

The effects of temperature, pH and water hardness on winter starvation of young-of-the-year smallmouth bass, Micropterus dolomieui Lacepede

Year-class strength in northern populations of smallmouth bass is strongly influenced by winter starvation of young-of-the-year. We examined starvation among young bass under both winter and summer light and temperature conditions. During starvation, body condition declines to a specific level and then the fish dies. Body condition at death is a well defined function of body size that remains relatively constant over a wide range of environmental conditions. Starvation rate varies systematically with body size, temperature, pH and water hardness. Available stored energy increases more rapidly with body size than starvation rate. Therefore, lifetime under starvation conditions tends to increase with increasing body size. The Q₁₀ for starvation rate over the temperature range 2.5-8° C is 2.2. Starvation rate increases as pH declines from 7.0-4.9: the rate at pH 4.9 is ∼ 1.25 times the rate at pH 7 Starvation rate decreases as Ca concentration increases from 1 mgl⁻¹ to 80mgl⁻¹: the rate at 80 mg Ca 1⁻¹ is ∼0.80 times the rate at 1 mgl⁻¹.     

Effect of ration size on growth and gross conversion efficiency of young lemon sharks, Negaprion brevirostris

Young lemon sharks, Negaprion brevirostris , were kept under controlled conditions in an aquarium and fed blue runner, Caranx crysos , at different ration levels. The relationship between feeding rate and growth rate was best described by a von Bertalanffy growth curve, which predicted a maximum growth rate of 140 kJ kg⁻¹ day⁻¹ (0·66% b.w. day⁻¹), a maintenance ration of 199 kJ kg⁻¹ day⁻¹ (1·06% b.w. day⁻¹), and losses due to starvation of -236kJ kg⁻¹ day⁻¹ (1·11% b.w. day⁻¹). The relationship between gross conversion efficiency ( K ₁) and feeding rate was also examined. K₁ ranged from - 64 to 25% and did not drop at high ration levels. Activity levels of both starved sharks and sharks fed at maintenance were not significantly different (0·2 body lengths s⁻¹). K ₁ values generated from both laboratory and field data suggest that young lemon sharks can convert food to new tissue as efficiently as teleosts.     

Depth equilibration by two predatory cichlid fish from Lake Malawi

The cichlid fish, Haplochromis polystigma and Haplochromis livingstonii are piscivorous ambush predators endemic to Lake Malawi, Africa. Experimentally it was found that large adult H. livingstonii could equilibrate to 38 m, but that juveniles were restricted to shallower depths. Mean depth attained by 8 H. polystigma was 45 m but two individuals exceeded the maximum simulated depth (59 m). H. livingstonii had a mean equilibration rate of 4–7 m day⁻¹ for the first 10 m declining to 2·4 m day⁻¹ thereafter. The mean rate of descent for H. polystigma was 3·8 m day⁻¹ for the first 10 m and 2·8 m day⁻¹ thereafter. The fish were decompressed at a rate of a 20% decrease every 12 h. Although cichlid fishes occur down to 200 m depth in Lake Malawi, experimental and field data indicate that the depth distribution of individual species is restricted and that the restriction is largely related to swimbladder physiology. All cichlid species so far tested equilibrate slowly to depth (2 to 5 m a day) and are not capable of rapid decompression.     

A PROPOSAL FOR A NEW RED ALGAL ORDER, THE THOREALES

Two abalone species: green Haliotis fulgens and yellow Halioti corrugata represent nearly 97% of the total production in the Mexican abalone fishery. It has been assumed that abalone feed on the kelp algae Macrocystis pyrifera. Regional hatcheries use this species as a main source of natural food. M. pyrifera does not occur at the southern limit of the distribution of abalone species along the Baja California Peninsula. In this study, growth rates of juveniles H. fulgens , 17.3 ± 2.2 mm shell length and 0.4 ± 0.2 g body weight, were evaluated. Juveniles were fed with common species in the benthic environments inhabited by abalone along the western coast of Baja California during 191 days. Three diets were based on algae: palm kelp, Eisenia arborea , giant kelp, M. pyrifera and Gelidium robustum , and one on seagrass, Phyllospadix torreyi. Shell length and body growth rates varied between 21.5 μm day⁻¹ and 2.2 mg day⁻¹ for E. arborea and between 45.9 μm day⁻¹ and 6.7 mg day⁻¹ for M. pyrifera. Higher specific growth rates (SGR) in length and weight were determined for M. pyrifera : 0.2% and 0.7% day⁻¹. Significant differences between values of juveniles fed M. pyrifera with the rest of the diets were found. The highest mortality (21%) was in juveniles fed the red algae G. robustum.     

Seasonal metabolism of a small, arboreal monitor lizard, Varanus scalaris, in tropical Australia

The field metabolic rates (FMR) and water fluxes of Varanus scalaris were measured during the wet and dry seasons by the doubly-labelled water technique. Seasonal measurements of standard (night-time) metabolism (SMR) and resting (daytime) metabolism (RMR) were made in the laboratory at 18, 24, 30 and 36°C, and maximal oxygen consumption was measured at 36°C on a motorized treadmill. This population was active throughout the year. In the wet season, the mean FMR was 7.8 kJ day⁻¹ (128.0 kJkg⁻¹ day⁻¹; mean mass = 66.4 g, n = 13), and during the dry season the mean was 5.0 kJ day⁻¹ (67.6 kJ kg⁻¹ day⁻¹; mean mass = 77.4 g, n = 17). The mean water flux rates for these animals were 3.6 and 1.2 ml day⁻¹, respectively (60.4 and 16.6 ml kg⁻¹ day⁻¹). The seasonal means of FMR and water flux were significantly different by ANCOVA ( P < 0.0001). Measurements of SMR and RMR were significantly higher in the wet season (ANCOVA: P < 0.0001), but we found no difference in the maximal oxygen consumption between seasons (ANCOVA: P = 0.6). The maximal oxygen consumption of the lizards on the treadmill (2.9 ml min⁻¹= 1.8 ml g⁻¹ h⁻¹), mean mass = 97.4 g, n = 16) was 20 times that of the SMR at the same temperature during the dry season, and 11 times that of the SMR during the wet season. The seasonal differences in FMR were attributable to: changes in SMR (12.2%) and RMR (16.4%); differences in night-time body temperatures (11.3) and daytime body temperatures (16.4%); and activity (broadly defined to include locomotion, digestion, and reproductive costs (43.7%).     

Food intake and growth in the Moses perch, Lutjanus russelli (Bleeker), with reference to predation on penaeid prawns

Juvenile Moses perch were fed various rations of penaeid prawn and pilchard foods at 26.4 and 28.7° C to elucidate feeding–growth relationships. Maintenance rations amounted to 5.0 and 3.8% of body weight per day (BW day^–1) on prawn and pilchard diets, respectively, at 26.4° C and 4.5% BW day ¹ for prawn at 28.7° C. This apparent reduction in maintenance ration at higher temperature is probably due to reduction in activity levels. Starvation weight loss, an indicator of resting metabolic rate, increased with temperature and exhibited a Q¹⁰ of 2.0 to 2.4.
Fish fed ad libitum once or twice per day at 26.4° C grew at 1.1 % BW day^–1 and ingested about 9% of their BW day^–1. At 28.7° C fish ingested about 8% of their BW day^–1 and grew 1 .0% BW day^–1. These growth rates are comparable to those of similar sized lutjanids in the wild. Since prawns comprise 64% of the diet of Moses perch in northern Australia, this level of consumption would require about 6% BW day^–1 of prawns. The relevance of these findings to the assessment of predator impact on prawns in Australian estuaries is discussed.     

Feeding and growth of early juvenile Japanese sardines in the Pacific waters off central Japan

Larval and early juvenile growth was backcalculated for individual Japanese sardines Sardinops melanostictus using the biological intercept method based on the allometric relationship between otolith radii and fish lengths. Sardines grew at 0·81 mm day⁻¹ during the larval stage. In the early juvenile stage, they grew from 32·3 to 45·4 mm fork length ( L ) over a 20-day period (0·64mm day⁻¹). Using the observed relationship between L and wet body weight ( W ), W = 0·00942 L ^2.99, W of the sardine juveniles was calculated to increase from 306 to 832 mg during the 20-day period. The carbon (C) requirement to achieve this growth in weight was estimated to increase from 5·7 to 9·6 mg day⁻¹. Stomach contents of the sardines were composed mostly of copepods (73%) and larvaceans (25%). Wet stomach content weight ( W_s ) was expressed by a power function of the W , W_s=0·731 W ^0·658. Carbon and nitrogen constituted 41·7 ± 1·5 and 10·0 ± 0·4% of the dry W_s , respectively. Stomach C content increased from 2·0 to 3·9 mg during the 20-day period. Three to four cycles of the daily turnover of stomach contents during the 16 h of daytime, corresponding to a gastric evacuation rate of 0·2–0·3 h⁻¹ under continuous feeding, met the C requirement to achieve the backcalculated growth in early juvenile sardines. The Kuroshio frontal waters seem to provide Japanese sardine juveniles with favourable growth conditions.     

The interaction of temperature and fish size on growth of juvenile halibut

Growth rate of individually tagged juvenile halibut was influenced significantly by the interaction of temperature and fish size. The results suggest an optimum temperature for growth of juvenile halibut in the size range 5–70 g between 12 and 15° C. Overall growth rate was highest at 13° C (1·62% day ⁻¹). At c. 5 g at the beginning of the experiment, fish at 16° C had the highest growth rate (3·2% day ⁻¹), but reduced this rate as they grew bigger. At 9 and 11°p C, growth rates were equal or only slightly lower during the later stages of the experiment, while the fish at 6° C showed significantly lower overall growth rate (0·87% day⁻¹). Optimal temperature for growth decreased rapidly with increasing size, indicating an ontogenetic reduction in optimum temperature for growth. Moreover, a more flattened parabolic regression curve between growth and temperature as size increased indicated reduced temperature dependence with size. Although individual growth rates varied significantly at all times within the experimental temperatures, significant size rank correlations were maintained during the experiment. This indicated an early establishment of a stable size hierarchy within the fish groups. Haematocrit was highest at the highest temperature while Na⁺/K⁺-ATPase activity was inversely related to temperature. There was no difference in plasma Na⁺, Cl⁻ and K⁺ concentrations among the temperature groups.     

Constraints of body size and swimming velocity on the ability of juvenile rainbow trout to endure periods without food

The hypothesis that body size and swimming velocity affect proximate body composition, wet mass and size‐selective mortality of fasted fish was evaluated using small (107 mm mean total length, L _T) and medium (168 mm mean L _T) juvenile rainbow trout Oncorhynchus mykiss that were sedentary or swimming ( c . 1 or 2 body length s⁻¹) and fasted for 147 days. The initial amount of energy reserves in the bodies of fish varied with L _T. Initially having less lipid mass and relatively higher mass‐specific metabolic rates caused small rainbow trout that were sedentary to die of starvation sooner and more frequently than medium‐length fish that were sedentary. Swimming at 2 body length s⁻¹ slightly increased the rate of lipid catabolism relative to 1 body length s⁻¹, but did not increase the occurrence of mortality among medium fish. Death from starvation occurred when fish had <3·2% lipid remaining in their bodies. Juvenile rainbow trout endured long periods without food, but their ability to resist death from starvation was limited by their length and initial lipid reserves.     

Growth, diet and metabolism of common wolf–fish in the North Sea, a fast–growing population

The von Bertalanffy growth parameters for common wolf–fish Anarhichas lupus in the North Sea were: male: L ∞=111·2 cm, t ₀=–0·43 and K =0·12; and female: L ∞=115·1 cm, t ₀=–0·39 and K =0·11, making this the fastest growing stock reported. Resting metabolic rates (RMR±S.E.) and maximum metabolic rates (MMR±S.E.) for six adult common wolf–fish (mean weight, 1·39 kg) at 5° C were 12·18±1·6 mg O₂ kg^–1 h^–1 and 70·65±7·63 mg O₂ kg^–1 h^–1 respectively, and at 10° C were 25·43±1·31 mg O₂ kg^–1 h^–1 and 113·84±16·26 mg O₂ kg^–1 h^–1. Absolute metabolic scope was 53% greater at 10° C than at 5° C. The diet was dominated by Decapoda (39% overall by relative occurrence), Bivalvia (20%) and Gastropoda (12%). Sea urchins, typically of low energy value, occupied only 7% of the diet. The fast growth probably resulted from summer temperatures approximating to the optimum for food processing and growth, but may have been influenced by diet, and reduced competition following high fishing intensity.     

Food intake and growth in the blue-spotted trevally, Caranx bucculentus Alleyne and Macleay 1877, with reference to predation on penaeid prawns

Blue-spotted trevally, Caranx bucculentus , were fed different rations of pilchard and prawn in order to investigate feeding and growth relationships. Maintenance rations at 25.5° C amounted to 3.7% B.W. day⁻¹ and 2.7% B.W. day⁻¹ for prawns and pilchards, respectively. Additional feeding experiments at 28.9° C yielded a maintenance ration of prawns of 3.8% B.W. day⁻¹, suggesting there is very little if any temperature effect on the feeding-growth relationship over the range studied. Fish fed twice or more each day consumed about 7.3 ± 1.4% B.W. day⁻¹.
Given the biomass of this trevally in Albatross Bay, Gulf of Carpentaria, and the contribution of prawns to its diet, we estimate consumption of commercial prawns at 25 ± 5 g.ha⁻¹ day⁻¹ or 11 g kg⁻¹ day⁻¹.     

Tissue depletion and energy utilisation during routine metabolism by sub-adult Tilapia rendalli boulenger

The amount of fat and protein used by young Tilapia rendalli during starvation can be quantitatively assessed and correlated to the condition of the fish. It was shown that fish in good condition used fat in preference to protein during catabolism, irrespective of the time period of starvation, but this rapidly reversed as condition declined and fish in medium and poor condition utilised more protein than fat to maintain routine metabolism. The amount of energy required during routine metabolism was not affected by the ratio of fat to protein used and a mean energy requirement for these fish (varying between 40 and 60 g in mass) was estimated as 45.03 J g-¹d^-1 at 23°C. This estimate of routine metabolic energy requirement can be equated to oxygen consumption using an oxy-energy coefficient of 13.68 J mg O₂^-1.     

Elevated oxygen uptake and high rates of nitrogen excretion in early life stages of the cobia Rachycentron canadum (L.), a fast-growing subtropical fish

Physiological energetics of cobia Rachycentron canadum were quantified for 18 to 82 days post-hatch (dph) hatchery-reared juveniles to better understand energy transformation and its implications in growth and survival. Mean oxygen consumption rates ( ; mg O₂ h⁻¹) of fish fed ad libitum and fish that were starved significantly increased with increasing wet mass (M; g), = 1·4291 M ^0·8119 and = 1·1784 M ^0·7833, respectively, with a significant reduction in mean metabolic rates of starved fish (19 to 27% specific dynamic action; SDA). Total ammonia nitrogen excretion rates ( A _MM, μmol h⁻¹) also scaled with M and significantly decreased after starvation. Mean mass-specific A _MM and urea excretion rates are the highest reported in the literature, with urea accounting for approximately half the total nitrogen excretion measured in both fed and starved fish. Relatively high energetic rates may allow cobia to develop rapidly into pre-juveniles and be less susceptible to predation and starvation at a comparatively early age.