David L. G. Noakes

Social dominance and interrenal cell activity in rainbow trout, Salmo gairdneri (Pisces, Salmonidae)

SynopsisThe relationship between standing in a dominance hierarchy and physiological stress was studied in rainbow trout. Individual fish were assigned relative dominance ranks, based on behavioral observations in a large, simulated stream tank. These ranks were compared to histometric measures of interrenal cell activity. Fish, isolated individually in the stream tank had significantly lower levels of interrenal activity than fish from the crowded holding tank. Groups of fish in the stream tank formed stable, linear dominance hierarchies. Interrenal activity correlated inversely with dominance rank, with the exception that top ranking fish had higher activity than expected. Possible cause and effect relationships are discussed.

Validation of Age Estimation for the Lake Sturgeon

Abstract The estimation of age of lake sturgeon Acipenser fulvescens by counting annuli in transverse sections of pectoral fin rays is validated through two methods: capture–recapture and examination of annuli laid down after injection of an oxytetracycline (OTC) marker. At first capture of each individual, the first ray of the right pectoral fin was removed. At recapture, 1–3 years later, the first ray of the left pectoral fin was removed. Differences between counts of annuli in rays collected at capture and at recapture were the same as the number of years that individual had been at large. At first capture lake sturgeons ranged in age and size from 4 years old and 43 cm fork length (FL) to 34 years and 115 cm FL. At recapture, they ranged from 6 years and 45 cm FL to 36 years and 122 cm FL. Fin ray sections of recaptured individuals previously injected with an OTC marker showed a discrete fluorescent band under ultraviolet light. The number of annuli outside this band corresponded to the number of year...

Low-Head Barrier Dams Restrict the Movements of Fishes in Two Lake Ontario Streams

Abstract The Great Lakes Fishery Commission (GLFC) is considering greater use of low-head barrier dams on stream tributaries of the Laurentian Great Lakes to control populations of sea lampreys Petromyzon marinus. The impact of these barriers on nontarget fishes is not known. A mark–recapture study on four Lake Ontario streams examined movements of fishes in streams with (barrier) and without (reference) low-head barriers. A significantly lower proportion of fishes moved across a real barrier on barrier streams than across a hypothetical barrier on reference streams (0.15 versus 0.50, respectively). The impact of the barriers on movement was more pronounced in spring and fall than in summer. However, the likelihood of fishes moving versus not moving between sample segments on either side of a barrier location (but not across the barrier) did not differ significantly between barrier and reference streams. The upstream (longitudinal) decline in species richness was greater for barrier streams than for refer...

Adaptive peaks and alternative foraging tactics in brook charr: evidence of short-term divergent selection for sitting-and-waiting and actively searching

Abstract Some recently emerged brook charr (Salvelinus fontinalis) inhabiting still-water pools along the sides of streams are sedentary and eat crustaceans from the lower portion of the water column. Others are more active and eat insects from the upper portion of the water column. We provide evidence that this divergent foraging behavior reflects short-term divergent selection brought about by intraspecific competition in the presence of alternative food sources. Rates of encounters and interactions between individuals were density dependent, and encounter and interaction events were closely timed with prey capture attempts. In addition, aggressive fish made more foraging attempts per minute than nonaggressive fish. Aggressive fish were also either inactive or very active, while nonaggressive fish exhibited intermediate levels of activity. Growth rate potential, an important component of fitness during the early life stages of brook charr, was assessed using tissue concentrations of RNA and found to be highest for sedentary fish and for active fish making frequent foraging attempts, and lower for fish exhibiting intermediate levels of activity. Our findings support contentions that individual behavior plays an important role during initial steps in the evolution of resource polymorphisms.

5 Ontogeny of Behavior and Concurrent Developmental Changes in Sensory Systems in Teleost Fishes

Publisher Summary This chapter elaborates the ontogeny of behavior and concurrent developmental changes in sensory systems in teleost fishes. Considerable changes in behavior occur during fish ontogeny. Weak contractions of the developing heart appear to be the first observable movements, occurring about one-third of the way through embryonic life. Ontogenetic changes in fish behavior may result from a number of interacting, proximate causal factors. These include developmental changes in the nervous system, nonneural physiological and morphological changes in the fish, changes in external stimuli, and experience. The ontogenetic changes in the retina and lens result in alterations in visual function, and thus have implications for visually mediated behavior. Photopic visual acuity, commonly defined as the minimum angle that a stimulus can subtend at the eye and still be resolved, is determined in part by the size and density of cones in the retina and their convergence onto higher-order retinal processing cells and in part by the focal length of the lens. The development of chemosensory systems and chemoresponses is also described in the chapter.

Distribution, community structure and production of fishes in the upper Speed River, Ontario: a preimpoundment study

SynopsisThe upper Speed River, on which a dam was under construction, was surveyed through fourteen qualitative and six quantitative collections to determine the distribution of fishes in the river above Guelph, Ontario and in a tributary, Luteral Creek. At the quantitative localities the removal method was used to estimate density and standing crop of all species. At three of these localities age and growth of the dominant species were determined and total ecological production calculated.Two approaches to the estimation of production for the 0–1 age class were compared and found to result in differences of 33–39% in the estimates of total production, thus illustrating the extent to which methodology may affect such estimatesThe dominant species in the river were, Semotilus atromaculatus, Notropis cornutus, Pimephales notatus, Rhinichthys atratulus, Hypentelium nigricans, Catostomus commersoni, Ambloplites rupestris, Micropterus dolomieui and Etheostoma flabellare. Density ranged from 11126 to 74765 individuals per hectare and standing crop from 32.4 to 190.0 kg ha−1. Production values at the three localities were 15, 19 and 54 kg ha−1 yr−1 , and are low compared with estimates for other fluvial systems. Comparison with a 1951 survey of the Speed River revealed considerable changes in the composition and distribution of fish species. The ranges of several cold-water species had contracted towards the headwaters, whereas several warm-water species had extended their ranges up the river

Aggressiveness and foraging mode of young-of-the-year brook charr, Salvelinus fontinalis (Pisces, Salmonidae)

SummaryYoung-of-the-year brook charr in streams use either an active or a sit-and-wait foraging tactic and exhibit a range of resource defense from territoriality to tolerating conspecifics. We use simple graphical models, based on encounter rate with drift and the theory of economic defendability, to predict qualitative changes in the aggressiveness and mobility of brook charr in relation to current velocity. Aggressiveness (percent of conspecifics eliciting an overt response) initially increases with increasing current velocity, as does drift rate and foraging rate. However, aggressiveness decreases at high current velocities, probably because of increased costs of defense at these velocities. In standing water areas, brook charr use primarily an active foraging tactic, but mobility (percent time spent moving) decreases rapidly as current velocity increases. These results are generally consistent with the simple graphical models. A literature survey suggests that the models can be generalized for most species of stream salmonids.

Size-based variation in somatic energy reserves and parental expenditure by male smallmouth bass, Micropterus dolomieu

Male smallmouth bass show size-based variation in both probability and timing of reproduction. The objective of this research was to determine seasonal and size-based patterns of depletion of energy reserves and determine if parental defense is related to males’ energy reserves. We sampled male smallmouth bass in the spring, during the parental care period and in the fall to measure energy reserves (lipid stores in muscle and viscera tissue) over a two year period. Energy stores, which were not built up before nesting, declined to a minimum level by the end of the parental care period. Small males had consistently lower energy reserves than larger males and did not utilize these reserves at the same rate during the parental care period. All parental males complimented endogenous energy reserves by feeding during parental care, however, small males appear to rely proportionately more on exogenous energy intake than do larger males. Parental defense by all sizes of males declined over the parental care period, the decline being the most obvious by small males. Small males’ lower energy budget may make them less effective parents and decrease their probability of survival over the following winter relative to larger males.

Environmental influences on territoriality of juvenile brook charr, Salvelinus fontinalis, in a stream environment

SynopsisJuvenile brook charr, Salvelinus fontinalis, defending territories in a laboratory stream channel changed their defensive tactics when fish numbers or water current velocity were increased. The associated increase in energy costs of territorial defense were apparently reduced by using relatively more lateral displays and fewer chases to repel intruders, and by decreasing territory size. Territory size tended to increase with food ration, although levels of aggression were not affected. These results emphasize the importance of energetic considerations in territoral defense in these fish, and are discussed in terms of current hypotheses regarding the resource base for territoriality.

Evidence for resource polymorphism in the lake charr (Salvelinus namaycush) population of Great Bear Lake, Northwest Territories, Canada

Abstract We sampled lake charr, Salvelinus namaycush, from Great Bear Lake, Northwest Territories, Canada, from June 30 to August 28, 2000. We assessed morphological variation in relation to stomach contents, age, and growth history of individual fish. We found significant differences in the morphology of insect-eating lake charr and fish-eating lake charr, specifically upper and lower jaw length, pectoral fin length, and caudal-peduncle depth. The age at capture did not vary between feeding types. However, otolith increment-width differences in the first 19 y of life were highly significant between feeding types. These results suggest that piscivorous lake charr grew faster than did insectivores. Our results support the hypothesis of trophic polymorphism in the lake charr in Great Bear Lake.