No abstract

Parental investment theory predicts that parents should adjust the level of care given to offspring relative to brood size and stage of brood development. This variation in parental care results from a trade-off between the reproductive value of the current brood and the reproductive return that the parent can expect to receive from future broods. Our study, carried out in Charleston Lake, Ontario, Canada, examined how handling stress and brood predation associated with catch-and-release angling influenced parental care behaviors and, ultimately, nest abandonment decisions of male smallmouth bass Micropterus dolomieu. Individuals were divided into six treatment groups: two different controls (n ϭ 10 and 11) and four test groups that were either angled and then released (n ϭ 11), had broods reduced manually to simulate predation (n ϭ 12), received a combination of angling and brood reduction (n ϭ 10), or had their brood size augmented through the manual addition of larvae (n ϭ 10). Exposing the fish to a model brood predator revealed that, after catch-and-release events, angled males were less willing or less able to defend their broods than were control fish. In addition, with or without angling, males subject to simulated brood predation were the least aggressive in defending their remaining broods. Moreover, the only treatment groups that showed substantially greater rates of nest abandonment were those that included simulated predation.

No abstract

Knowledge of animal spatial ecology is essential for the design and siting of proposed aquatic protected areas (APAs), as well as the assessment and monitoring of existing ones. Acoustic telemetry is one of the primary tools for the assessment of animal movements in aquatic systems through either manual tracking or the establishment of fixed receiving stations. Recent technological developments in code division multiple access (CDMA) acoustic telemetry now enable the simultaneous real-time monitoring of numerous individual fish at fine time scales providing APA researchers with a robust new tool. Fish can be positioned in three-dimensions with sub-meter accuracy in both deep and shallow waters. Here, we describe a whole-lake environmental observatory that includes a 13-hydrophone acoustic telemetry array that has been used to monitor the position of 22 tagged fish at 15 sec intervals. Although we use a freshwater fish and environment as a case study, this telemetry system is equally useful for marine environments including under-ice. We evaluate the applicability of CDMA MAP technology to address pressing questions in applied APA research. The CDMA MAP system provides the flexibility to collect information at multiple spatial-temporal scales, responding to the varied levels of detail and precision required for different applications in APA research. When combined with the suite of other telemetry and monitoring approaches available, CDMA MAP technology will enable researchers to document the spatial ecology essential for improving APA science. Furthermore, because numerous animals from different trophic levels can be tracked in real time, CDMA MAP technology will also aid in our understanding of complex community-level dynamics consistent with the shift towards ecosystem-based APA management.

Annual reproductive surveys monitored nesting location, reproductive success and the age and size of individually tagged male smallmouth bass Micropterus dolomieu that reproduced in Millers Lake, a 45 ha widening of the Mississippi River, Ontario, and in a 1Á5 km pool and riffle section of the river directly upstream. The vast majority of males displayed fidelity to either the river or the lake as reproductive habitat throughout their lifetimes. Nearly, half of the males that reproduced in successive years exhibited strong nest-site fidelity by nesting within 20 m of their previous year's nest site. In most years, when compared to those in the lake, reproductive males in the river differed significantly in reproductive characteristics including age and size at maturation and nesting success rates. A 3 year telemetry project identified two distinct habitat use patterns: lake-resident fish remained in the lake throughout the year and potamodromous individuals migrated from the lake to upriver spawning habitat in the spring and then returned to the lake prior to the onset of winter. Integration of habitat use and reproductive data suggests that there are significant differences in the life-history strategies of fish that reproduce in the river v. the lake.

No abstract

A whole-lake acoustic telemetry array was utilized to monitor the three-dimensional position of 20 largemouth bass (Micropterus salmoides). Code division multiple access (CDMA) technology enabled the simultaneous monitoring of the 20 transmitters (equipped with pressure and temperature sensors) at 15 s intervals with sub-meter accuracy. Fish were monitored between

1978. Predatory responsesofa raptorguild tochangesin prey density. Can. J. Zool. 56: 2565-2572. The responses of a guild of open-country birds of prey to changes in prey density were studied on a simple island habitat in southern Ontario. Numerical responses were conspicuous in all species, while functional responses were weak. Individual raptor speciesdisplayed characteristic responses, differingfrom others in intensity and aspects of seasonality related to breeding versus wintering. Yet a basic similarity in the form of response for all species present at any one season, and a complementarity of responses of species present through the changing seasons, resulted in an overall guild level pattern of numerical and functional response of predators to changes in prey density. The synchronous fluctuations of predator and prey densities observed are similar to those of arctic areas and unusual for the temperate regions where the study was conducted. Characteristics of the predator and prey assemblages and features of the study site were important in determining the type, the intensity, and the level (species or guild) at which the responses were exhibited. PHELAN, F. J. S., et R. J . ROBERTSON. 1978. Predatory responses of a raptor guild to changes in prey density. Can. J. Zool. 56: 2565-2572. Les reponses d'une bande d'oiseaux de proie aux changements de densite des proies, dans un espace decouvert, ont fait I'objet d'une etude dans un habitat insulaire du sud de I'Ontario. Les reponses numeriques sont evidentes chez toutes les especes, mais les reponses fonctionnelles sont faibles. Les reponses des divers rapaces sont spkcifiques, differant les unes des autres par leur intensite et par certains aspects temporels relies a la saison de reproduction et i I'hiver. La similitude fondamentale entre les reponses de toutes les especes presentes en une saison donnee et la complementarite des reponses des especes presentes d'une saison a I'autre font qu'il existe chez les predateurs, au niveau de la bande, des types de reponses numeriques et fonctionnelles aux changements de densite des proies. Les fluctuations synchronisees des densites, chez les proies et chez les predateurs, sont sernblables Bcelles qui existent dans les regions arctiques; elles sont etonnantes pour une region temperee comme la region experimentale. Les caracteristiques des associations de predateurs et de proies et la structure du site experimental sont des facteurs importants lors de la determination du type et de I'intensite des reponses ainsi que du niveau (espece ou bande) auquel elles se manifestent.