Specific growth rate and proximate body composition of Atlantic cod (Gadus morhua L.)

The effect of growth rate and maturation on the proximate composition and energy content of Atlantic cod, Gadus morhua L., was investigated over 10 months for each of two consecutive years, 1978–1980 at 5 and 8 °C. Relative energy and lipid content of whole cod increased with specific growth rate for all three sampling periods (November, January, March), each at 5 and 8 °C. Relative water content decreased with specific growth rate and temperature, and was lower in March than in January and November. Relative protein content was positively correlated with specific growth rate, but to a lesser degree than with temperature and age. Relative ash content was negatively correlated with specific growth rate. The effect of season and temperature on the proximate content of gonad, liver, muscle, and carcass was also determined. The major energy and lipid source in cod was the liver. Energy, lipid, and water were highly correlated to each other, and regressions are provided to allow for their prediction, given one of the components. Energy budgets for cod at 5 and 8 °C are calculated and the effect of increased ration size on the budget is estimated. The prediction of short-term specific growth rates of cod from the proximate composition is proposed. The proximate composition of cod is affected by growth rate and thus feeding level, and in turn directly affects behaviour. The relative proximate content of maturing and immature 3-yr-old cod was not found to be significantly different. Keywords: specific growth rate; proximate; bioenergetics; Atlantic cod; energy budget; temperature; season     

Rates of oxygen consumption by Thais (Nucella) Lapillus (L.)

Oxygen consumption by Thais varied seasonally with higher values in summer than in winter. This seasonal difference was due in part to the effects of temperature and in part to those of feeding. During feeding, rates of oxygen consumption were high, but declined in the period between meals. There was little evidence of acclimation of oxygen consumption to changes in temperature; low (winter) rates of consumption were more sensitive to increases in temperature than were high (summer) rates. A polynomial expression, including terms for temperature and ‘time since last meal’, was derived for the constant a′ in the allometric equation relating oxygen consumption (_o2) to dry body weight: _o2 = a′.W^0.511.     

The escape response of food-deprived cod larvae (Gadus morhua L.)

The escape response of Atlantic cod larvae (Gadus morhua) 25 and 47 days post hatch (dph) - either fed or deprived of food for three days - was studied. Larval escape responses were provoked by water movement from the suction of a fixed-position pipette. Escape latency, distance, speed, burst speed, and vertical and lateral escape angles were quantified using motion tracking software designed for 3-D silhouette video recordings. Escape performance, expressed as escape distance and escape speed, improved with age. The escape angles were normally distributed and highly variable, ranging from − 170° to 170° and − 40° to 105° for lateral and vertical escape angles respectively. No food deprivation-induced effects in any of the behaviours were found, suggesting that there are no condition-related behavioural effects (size-independent effects) in escape response performance after 3 d of food deprivation. This may reflect a negligible difference in the cost/benefit equation for fed vs. food-deprived larvae in performing an escape response when under attack.     

The effect of growth rate,size, and season on oocyte development and maturity of Atlantic cod (Gadus morhua L.)

The effect of growth rate, body weight, age, and season on ovarian development and maturation was investigated for Atlantic cod (Gadus morhua L.) reared in the laboratory over 10 months, for each of two consecutive years, 1978–1980. Cod were also collected from the Gulf of St. Lawrence, the Scotian Shelf, Georges Bank, the Flemish Cap, and the N.E. Newfoundland Shelf.The state of maturity was recognized by oocyte size. Stage I oocytes did not vary in size with growth rate, season, age, or maturity, while the size of stage II oocytes was positively correlated with maturity and negatively correlated with maximum stage of development achieved. Ovarian wall thickness was positively correlated with age and maturity.The frequency distribution of stage I and II oocytes distinguished the state of maturation, with cod that would mature by the next spawning season having a minimum of 20% ($\text{x}\text{?}\text{= 42\%}$) of their oocytes at stage II or greater level of development.Maturing 3-yr-old cod had greater life specific growth rates than immature 3-yr-olds, but growth rates during the third year itself were not significantly different. A hypothesis of a three-part density-dependent mechanism controlling fecundity is postulated. Future reductions in partial recruitment and total fecundity are predicted for the Gulf of St. Lawrence cod stock based on calculated growth rates for Gulf cod in 1979.     

Copper metabolism in the plaice, Pleuronectes platessa (L.)

Copper metabolism in a teleost, the plaice, Pleuronectes platessa (L.) from a natural environment has been studied. Distribution in the various tissues of the metal and of five key copper-dependent enzymes: ceruloplasmin EC 1.16.3.1; Superoxide dismutase EC 1.15.11; tryptophan oxygenase EC 1.13.1.12; cytochrome oxidase EC 1.9.3.1 and monoamine oxidase EC 1.4.3.4 have been determined. The copper distribution was found to be similar to that in mammals with the greatest concentrations in the brain and heart. Distribution of the copper enzymes is also similar to that found in mammals. A preliminary characterization of the copper enzymes showed that plaice cytochrome oxidase has a pH maximum 2 pH units more alkaline than the mammalian enzyme and that plaice tryptophan oxygenase is more sensitive to heat denaturation than the mammalian enzyme. The present data form a base-line against which studies on factors affecting the copper metabolism in a teleost can be assessed.     

Effects of hypoxia and body size on the oxygen consumption of the bivalve Arctica islandica (L.)

The relationship between oxygen consumption and body weight has been examined in Arctica islandica (L.).Large Arctica exhibit a high degree of respiratory independence under hypoxic conditions; like other species studied, respiratory independence increases markedly with increasing body size. Respiratory independence can also be modified by temperature and physiological condition and it is concluded that the division of species per se into oxygen regulators and oxygen conformers is not merited. These terms describe only the extremes of what is a variable capacity to maintain respiratory independence during hypoxia.     

Ventilation and oxygen consumption in the hagfish, Myxine glutinosa L.

Ventilation was measured directly in the hagfish, Myxine glutinosa L., by means of an electro-magnetic blood flowmeter. Ventilatory flow and frequency increased from 0.86 ± 0.27 ml·min^?, and 18.2 ± 5.1·min^?, respectively, at 7°C to 1.70 ± 0.20 ml·min^?, and 70.1 ± 9.5·min^? at 15 ·C.Standard oxygen consumption,V?O₂, was measured in non-buried hagfish. V?O₂ was 0.57 ± 0.17μl O₂·g^?1·min^?1 at 7°C, and 0.85 ± 0.12μl O₂·g^?1·min^?1 at 15°C.     

Hypoxic avoidance behaviour in cod (Gadus morhua L.): The effect of temperature and haemoglobin genotype

Hypoxia can influence fish growth, survival and on larger scales, population structure. These effects may be influenced by water temperature, and may vary intra-specifically with genotype. In Atlantic cod (Gadus morhua L.), the two haemoglobin homozygotes (Hb-I?11 and Hb-I?22) vary in oxygen affinity at different temperatures, which is thought to correspond to variation in hypoxia tolerance. We therefore tested if hypoxic avoidance behaviour in cod 1) depends on ambient temperature and 2) is modified by haemoglobin genotype. In a laminar flow choice box, we subjected juvenile cod to an initial phase of non-escapable hypoxia, and a subsequent recovery phase, where one habitat was kept at 20% O₂ saturation while the other was raised in steps to full saturation. The experiment was performed at 5 and 15 °C with Hb-I?11 and Hb-I?22 cod. Cod responded to inescapable hypoxia by reducing their overall swimming speed and then, at the initial levels of the recovery phase, avoiding the most hypoxic habitat, irrespective of temperature or genotype. Fish recovered quickly as O₂ levels increased, as evidenced by increased swimming speed and time spent in the most hypoxic habitat. The avoidance response depended strongly on temperature: the relative reduction in speed and avoidance of the most hypoxic habitat was more pronounced at 15 than at 5 °C. During the recovery phase, stressed fish initially maintained a higher swimming speed in the most hypoxic habitat. However, as O₂ increased, swimming speed in both habitats converged. This point of convergence occurred at a lower O₂ saturation at 5 °C. Fish ventilation rate in inescapable hypoxia was also higher at 15 °C. Haemoglobin genotype did not influence either ventilation rates or the nature of the hypoxic avoidance response at either temperature, but Hb-I?11 cod swam faster than Hb-I?22 cod in normoxia at 15 °C. Our results indicate that increased temperature limits the ability of cod of both haemoglobin genotypes to exploit hypoxic habitats. This may have negative future consequences for coastal cod stocks in light of increasing global temperatures and eutrophication in coastal waters.     

Orientated growth of Membranipora membranacea (L.) on the thallus of Saccorhiza polyschides (Lightf.) Batt.

Orientated growth is described in colonies of Membranipora membranacea (L.) growing on the large brown seaweed Saccorhiza polyschides (Lightf.) Batt. On average, 60% of the growth of the colonies was directed proximally along the long axis of the plant, irrespective of the region of the plant on which the colonies were growing or their proximity to its primary meristem. These results seem to rule out the possibility that orientated growth in Membranipora is a response to an age dependent polarity in the host plant, since the tissue ages in opposite directions in the lamina and stipe yet the growth of Membranipora is orientated in the same direction on both. The possibility that directional growth in this species may be a rheopositive response is discussed.     

An arabinogalactan from the fibres of cotton (Gossypium arboreum L.)

An acidic arabinogalactan has been isolated from fibres of the cotton plant (Gossypium arboreum L.) at the stage of intensive secondary-wall formation. The polysaccharide contains arabinose, galactose, rhamnose, and glucuronic acid residues in the molar ratios 1:1.2:0.1:0.2. Periodate oxidation and methylation studies showed that there is a main chain of (1→3)-linked galactopyranosyl residues to which side chains are attached at O-6. The side chains consist of (1→6)-linked galactopyranosyl residues substituted at O-3 by (1→5)-linked arabinofuranosyl chains. Terminal galactopyranosyl, rhamnopyranosyl, and glucopyranuronosyl groups are also present. Enzymic hydrolysis showed that the configurations of the galactose and arabinose residues are d and l, respectively.     

Effect of somatic and otolith growth rate on stable isotopic composition of early juvenile cod (Gadus morhua L) otoliths

The relative amounts of the stable isotopes of carbon and oxygen in fish otoliths can be used to reveal the environmental history experienced by the fish. This requires that the relative amounts of the isotopes are deposited in equilibrium with the surrounding environment, or that the offset from this equilibrium is known and can be quantified. It is known that carbon isotopes in biogenic carbonates are a mixture of carbon from the seawater and metabolically derived carbon, but the effect of the somatic growth rate of the fish is still unclear. The possible effect of otolith growth rate and fractionation of both carbon and oxygen isotopes are also not established. We carried out a controlled laboratory experiment where we reared cod (Gadus morhua L.) larvae and early juveniles at two temperatures (6 and 10 °C) and generated different growth rates within each temperature by manipulation of prey levels. The otoliths of the resulting fish were analysed for carbon and oxygen isotopes. We found no effect of otolith precipitation rate on fractionation of either carbon or oxygen isotopes. However, there was a depletion of ¹³C in the otoliths of fish with elevated metabolism. The proportion of metabolically derived carbon in the otoliths was estimated to be 28-32%. Our results suggest that measurements of oxygen isotopes in otoliths can be a reliable tool to estimate ambient temperature since the oxygen isotopes seem to be deposited in the otoliths independently of kinetic and metabolic effects. Fractionation of carbon isotopes in otoliths on the other hand can give valuable insight into metabolism and feeding pattern of fish.     

Brown shrimp (Crangon crangon, L.) functional response to density of different sized juvenile bivalves Macoma balthica (L.)

Variability in infaunal bivalve abundance in the Wadden Sea is largely determined by recruitment variability. Post-settlement, but pre-recruitment bivalve mortality is high and related to the occurrence of their most abundant predator, the brown shrimp Crangon crangon. To investigate if the mortality patterns of newly settled bivalves can be explained by the foraging behavior of brown shrimp, we carried out experiments on shrimp functional response to three size classes of juveniles of the Baltic Tellin Macoma balthica. The functional response curves for all three prey sizes (0.62 mm, 0.73 mm, and 0.85 mm) were the hyperbolic Holling's type II. The attack rate was highest for the smallest prey size (a = 0.31, medium and large prey a = 0.22); the handling time was longest for the largest prey size (T_h = 29 s, small and medium prey T_h = 15 s). Thus, a large body size is advantageous for the bivalves over the whole density range. Knowledge of individual foraging behavior is needed to model predation mortality of bivalves. The consumption rates in the experiment were theoretically high enough to account for M. balthica mortality in the field.     

Comparative study of nitrogen and oxygen metabolism enzymes in Yugoslav cultivars of alfalfa (Medicago sativa L.)

Four Yugoslav cultivars of alfalfa were investigated in order to determine nitrogen fixing (nitrogenase), nitrogen assimilation (nitrate reductase, glutamine synthetase, glutamate dehydrogenase) and antioxidant (Superoxide dismutase, catalase, peroxidase) enzymes activities. The level of lipid peroxidation and protein content were also investigated. On the basis of the results obtained a resistant cultivar with high nitrogen fixing and a cultivar with high nitrogen assimilation abilities were chosen. The cultivar with high nitrogen fixing ability had high activities of nitrogenase, Superoxide dismutase, peroxidase and catalase, and also a low level of lipid peroxidation. The cultivar with high assimilation ability had high activities of nitrate reductase, glutamine synthetase and glutamate dehydrogenase and high soluble protein content.     

The effect of rutin on growth,fecundity and food utilization in Acheta domesticus (L.)

Growth of larvae of Acheta domesticus to the adult stage on an artificial diet was improved significantly by the addition of 0.1% rutin to the diet. Fecundity was also increased. These results cannot be explained by a stimulation of feeding by rutin. They appear to be due to an effect on the utilization of the food, brought about possibly by an action on gut movement, on gut transport or on the microbiol flora.     

The respiratory responses of the dog cockle Glycymerisglycymeris (L.) to declining environmental oxygen tension

The subtidal bivalve Glycymeris glycymeris (L.) exhibits a high degree of respiratory independence in conditions of declining environmental oxygen tension. In contrast to other bivalves previously studied, the index of respiratory independence, $\text{K}{}_1\text{K}{}_2$ decreases with increasing weight specific oxygen consumption indicating that small Glycymeris are better regulators of oxygen consumption than large Glycymeris.The respiratory responses of Glycymeris to hypoxia include a small initial increase in ventilation, brought about by increasing the percentage of time spent pumping and a large increase in oxygen utilization. Heart activity is elevated, principally through a large increase in the amplitude of heart beat, which suggests increased perfusion of the respiratory surfaces. The ventilation : relative perfusion ratio, therefore, declines over the range of oxygen tension that respiratory independence is maintained.The respiratory mechanism of Glycymeris is compared with that previously described for other bivalves and it is concluded that there are no clearcut differences between the respiratory responses to hypoxia of intertidal and subtidal species.