F. W. H. Beamish

Heat Increment: A Static or Dynamic Dimension in Bioenergetic Models?

Abstract Bioenergetic models of growth endeavor to integrate food-processing transactions with energy expenditures imposed by abiotic and biotic factors. Some components of these models have lagged behind others in the synthesis of new information. A case in point is heat increment, a measure of metabolic work primarily for the postabsorptive processes that follow the ingestion of food. Importantly, the energy requirements for grasping, chewing, and swallowing food are technically distinct from those for heat increment but are experimentally difficult to separate from them. In order to take special account of these mechanical aspects, we suggest modifying the term “heat increment” (also known as specific dynamic action) to the less-precise “apparent heat increment.” Bioenergetic models invariably incorporate the assumption that apparent heat increment, relative to food intake, is independent of other variables. Laboratory studies have revealed that apparent heat increment is not always a fixed proportion ...

Effects of Time and Velocity Increments on the Critical Swimming Speed of Largemouth Bass (Micropterus salmoides)

Abstract Critical swimming speed was measured for largemouth bass and found to be related to the increments of both time and water velocity. Critical speed decreased with increase in time interval, and reached a peak and declined thereafter with increasing velocity increment.

Dynamics of dietary methylmercury in rainbow trout, Salmo gairdneri

Abstract Rainbow trout, Salmo gairdneri, were fed diets containing 0, 25, 45, 75 or 95 mg Hg · kg−1 methylmercury for 84 days at meal sizes of I and 2% · day−1 and to satiation. Uptake and depuration of methylmercury was followed in fish fed fixed rations by feeding some of these fish diets containing 203Hg-labeled methylmercury. Appetite, apparent digestibility of ration and growth decreased in fish fed diets containing added methyl-mercury. Whole body mercury concentrations of trout fed diets containing added methylmercury increased throughout the first 56 days of feeding, then generally stabilized from 56–85 days. The total amount of mercury in the fish, however, increased throughout the 84 days. Trout generally assimilated 70–80% of the labelled methylmercury they were fed. Among fish fed the 75 ing Hg · kg−1 diet for 9 wk, assimilation decreased to Labeled methylmercury was depurated faster in fish fed the higher meal size. Methylmercury depuration in rainbow trout would thus seem related to metabolic rate. Trout fed diets containing added methylmercury depurated labeled methylmercury more rapidly than fish fed diets without added methyl-mercury, suggesting that methylmercury depuration may be induced by continued exposure to the compound.

Swimming performance of adult sea lamprey, (Petromyzon marinus), in relation to weight and temperature

Abstract Distance (m) sea lampreys, Petromyzon marinus, swam increased with weight (2.4–106.9 g) but at a decreasing acceleration for a fixed velocity and temperature. Distance declined with increase in swimming speed between 20–60 cm/sec at a decreasing acceleration. The greatest distance was recorded for the largest lampreys at the lowest swimming speeds. Distance increased with temperature between 5–15 C. Performance of sea lampreys was less than that for teleosts which may be related to differences in their morphology.

Age Determination for Lampreys

Abstract Age structures of several populations of parasitic and nonparasitic lampreys were estimated from statolith band number and length-frequency distributions. In larval populations of the parasitic sea lamprey Petromyzon marinus and nonparasitic American brook lamprey Lampetra appendix, which display strong seasonal patterns ofgrowth, one narrow dark band or annulus and one broad opaque band was produced each winter and summer, respectively. The formation of an annulus during slow growth was validated in two populations of sea lampreys with a chemical tissue marker, oxytetracycline. Length-frequency distributions required large samples to identify age groups, and the older age groups within a population were often difficult to distinguish because of overlap in size ranges. Thus, the assignment of age to an individual from its total length was likely to be imprecise unless that individuals length was close to the modal length of an age group. Some discrepancies in the assignment of population age str...

Initiation of feeding and salinity tolerance in the pacific lamprey Lampetra tridentata

Changes in salinity tolerance were determined during metamorphosis in Lampetra tridentata. Lampreys in Phase 5 of metamorphosis were unable to withstand salinities>13.4‰S, while those in Phase 6 survived direct transfer to sea water (30‰S). This abrupt change in tolerance coincided with the opening of the foregut lumen. Parasitic feeding began at the end of Phase 7 of metamorphosis following the completion of tooth development.

Changes in Blood Chemistry and Critical Swimming Speed of Largemouth Bass, Micropterus salmoides, with Physical Conditioning

Abstract Physical conditioning at swimming speeds of 2 and 3 body lengths per second for periods up to 30 days increased critical swimming speed by as much as 15% over that found for unconditioned fish. Haemoglobin increased significantly with conditioning, suggesting an enhancement of aerobic capacity. Conditioning did not, in general, increase the production of lactate dehydrogenase in blood serum. Following periods of swimming at critical speeds, blood volume decreased in unconditioned bass but with conditioning remained relatively stable.

Factors Affecting Larval Sea Lamprey Growth and Length at Metamorphosis in Lampricide-Treated Streams

Abstract Larval sea lampreys Petromyzon marinus in seven lampricide-treated streams were studied to assess the effects of density and abiotic factors on growth, length at metamorphosis, and age at metamorphosis. Support for density-dependent growth was not found in these streams. A linear relationship between total length and age was found for all populations. The daily growth of larvae in lampricide-treated streams was similar to that of populations that were never exposed to lampricide. Furthermore, the growth of stocked residual populations did not increase following a lampricide-induced reduction in larval density. Differences in growth and length at metamorphosis among these streams were accounted for by abiotic factors. Larval growth was highest in streams with an annual water temperature around 8°C, moderate discharge (0.5–2.0 m3/s), and high conductivity (>300μS). Length at metamorphosis, on the other hand, was inversely related to conductivity, annual discharge, and annual mean temperature. A mod...

Notes: Age Discrimination and Statolith Diversity in Sea Lamprey from Streams with Varying Alkalinity

Abstract The diversity of statoliths and changes in statolith length were examined in larval and metamorphosing sea lampreys Petromyzon marinas from four streams in Ontario. In midsummer, increases in statolith lengths were similarly and positively correlated with larval total lengths in the four streams. Statoliths from larval and metamorphosing lampreys collected from Lynde and Farewell creeks in June and September displayed typical alternating opaque and translucent bands. The number of opaque bands, or annuli, provided reliable age estimates when compared with length-frequency distributions. In July and September, statoliths from some larval and metamorphosing lampreys collected from West Root River and Cannon Creek were either absent or did not have typical bands, hence they did not always provide reliable ages. The diversity of statoliths appears to be related to ambient calcium ion concentrations, especially during periods of rapid larval growth. The use of statoliths is sometimes the only method t...

Ambient ammonia, diet and growth in lake trout.

Abstract Juvenile lake trout were exposed to ambient free (un-ionized) ammonia concentrations of 0, 99, 198 and 297 μg NH3N 1−1 for 60 days and fed one of two diets which were similar in energy concentration. Diet did not influence food intake at ammonia concentrations of 0, 99 and 198 μg NH3N 1−1. Food intake was unaffected by ammonia concentrations of 0 and 99 μg NH3N 1−1 and was only temporarily reduced when ammonia was 198 μg NH3N 1−1. Trout exposed to 297 μg NH3N 1−1 consumed significantly less food than fish exposed to the lower concentrations of ammonia. Food intake did not differ with diet during the first 30 days of exposure to 297 μg NH3N 1−1 but during the final 30 days, it was higher for trout fed the low protein diet. Growth, measured as a change in live body weight was not influenced by ammonia concentrations of 0, 99 and 198 μg NH3N 1−1 but declined significantly at 297 μg NH3N 1−1. Weight gain tended to be larger for trout fed the high protein diet. Efficiency of protein-N gain was greater for trout fed the low protein diet, presumably as a consequence of a sparing effect afforded by high dietary lipid. Efficiency of protein-N gain was significantly reduced among lake trout exposed to the highest concentration of ammonia. Mortalities were observed only among trout exposed to the highest concentration of ammonia.