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  • 1
    Electronic Resource
    Electronic Resource
    Food ration and condition affect early survival of the coral reef damselfish, Stegastes partitus (1999)
    Springer
    Oecologia 121 (1999), S. 364-368 
    Details
    ISSN: 1432-1939
    Keywords: Key words Condition ; Coral reef fish ; Food ration ; Post-settlement mortality ; Predation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The supply of larvae is a major determinant of population and community structure in coral reef fishes. However, spatial and temporal variation in condition (i.e. quality) of potential recruits, as well as their density (i.e. quantity), may influence survival and growth of juveniles. We conducted an experiment to test whether recent feeding history could affect growth, condition and post-recruitment survival in a Caribbean damselfish, Stegastes partitus. Fish were collected soon after settlement, and fed either low or high rations in aquaria for 7 days. Fish fed the high ration grew faster in aquaria and were in a better condition (higher total lipids and Fulton’s condition factor) at the end of the feeding period. Subsequently, we released 50 fish in 25 pairs (one fish subjected to low rations, the other to high rations) on a Bahamian coral reef and monitored survival for 10 days. Survivorship of high-ration fish was double that of low-ration fish (80 vs 40% over 10 days). However, low-ration fish that survived 10 days were of similar condition and grew at similar rates to high-ration fish, suggesting that short-term ration differences may not persist in surviving fish. Laboratory experiments showed that low-ration fish were taken by piscivorous fishes before high-ration fish, indicating that differential predation may account for survival differences. This study highlights the potential of feeding history and condition to affect the relationship between patterns of larval arrival at reefs, and subsequent juvenile and adult population densities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050940
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Exploitative compensation by subordinate age-sex classes of migrant rufous hummingbirds (1993)
    Springer
    Behavioral ecology and sociobiology 33 (1993), S. 305-312 
    Details
    ISSN: 1432-0762
    Keywords: Intraspecific dominance ; Foraging ecology ; Migration ; Stopovers ; Hummingbirds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The three age-sex classes of rufous hummingbirds (Selasphorus rufus) that directly interact on southward migratory stopovers in our California study system differ in territorial ability and resource use. Immature males are behaviorally dominant to adult and immature females and defend the richest territories. Here, we test the hypothesis that the territorially subordinate age-sex classes compensate exploitatively for their exclusion from rich resources. Our results show that females were able to accumulate energy stores at rates comparable to males despite their subordinate territorial status. Territorial females gained body mass at the same rate and in the same pattern as males, and resumed migration at the same body masses. Moreover, during periods when birds were nonterritorial and used dispersed resources, adult and immature females maintained or gained body mass, whereas immature males lost mass. We suggest that females may be energetically compensated by (1) lower costs of flight incurred during foraging and defense, resulting from their lower wing disc loading, and (2) greater success at robbing nectar from rich male territories, resulting from duller coloration (immature females), experience (adult females), and, possibly, hormonal differences. In the future, experiments will be necessary to distinguish the various hypotheses about the mechanisms involved in compensation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00172928
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  • 3
    Electronic Resource
    Electronic Resource
    Interference asymmetries among age-sex classes of rufous hummingbirds during migratory stopovers (1993)
    Springer
    Behavioral ecology and sociobiology 33 (1993), S. 297-304 
    Details
    ISSN: 1432-0762
    Keywords: Intraspecific dominance ; Territoriality ; Migration ; Stopovers ; Hummingbirds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Three age-sex classes of rufous hummingbirds (Selasphorus rufus) overlap temporally and defend feeding territories during migratory stopovers in the Sierra Nevada of California. We demonstrate that these classes differ in their ability to secure and maintain high-quality feeding territories for refueling, and that these differences result in differences in resource use. Data on acquisition of territories, territory characteristics, and responses of territory owners to intruders suggest that several mechanisms are involved in determining dominance, involving sex- and age-related differences in wing disc loading, coloration, and experience. We discuss the implications of these results for understanding intraspecific variation in migration strategies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00172927
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  • 4
    Electronic Resource
    Electronic Resource
    Why hummingbirds have such large crops (1991)
    Springer
    Evolutionary ecology 5 (1991), S. 405-414 
    Details
    ISSN: 1573-8477
    Keywords: Foraging behaviour ; meal size ; crop size ; optimization ; energetics ; territoriality ; intruders ; hummingbirds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Male Anna's Hummingbirds (Calypte anna) defend territories that contain a predictable food source, floral nectar. For such a hummingbird, the meal size that maximizes long-term net energy intake is less than the maximal crop volume. Smaller meals must be consumed more frequently, but larger meals increase body mass and therefore flight cost. Individuals without territories or with inadequate territories do not have easy access to nectar and intrude on territories owned by otherC. anna, where they may be chased at nay time. It was predicted that these intruders should minimize the number of potentially risky intrusions necessary for maintenance by ingesting as much nectar as possible whenever they manage to feed without being chased (usually when owners are temporarily absent). Therefore, relative to uninterrupted feeding by owners, uninterrupted intruders should feed longer and take larger meals. Field observations supported these predictions. Intruders apparently filled their crops in all seasons, whereas owners ingested smaller amounts (0.21–0.22 ml) and fed for lengths of time consistent with the prediction of an optimization model (0.21 ml). Thus, owners may energetically optimize meal size whereas intruders fill their crops whenever they are not chased. Under most conditions, hummingbirds only fill their crops one-tenth to one-third full, leading to the question why hummingbirds have such large crops. This study demonstrates that a large crop volume may be of survival value when an individual lacks a territory or has inadequate access to resources and must poach on others' territories.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02214157
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  • 5
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    Current velocity and catch efficiency in sampling settlement-stage larvae of coral-reef fishes (2021)
    In:  http://aquaticcommons.org/id/eprint/15220 | 403 | 2014-06-01 19:00:52 | 15220 | United States National Marine Fisheries Service
    Details
    Publication Date: 2021-07-04
    Description: Light traps and channel nets are fixed-position devices that involve active and passive sampling, respectively, in the collection of settlement-stage larvae of coral-reef fishes. We compared the abundance, taxonomic composition, and size of such larvae caught by each device deployed simultaneously near two sites that differed substantially in current velocity. Light traps were more selective taxonomically, and the two sampling devices differed significantly in the abundance but not size of taxa caught. Most importantly, light traps and channel nets differed greatly in their catch efficiency between sites: light traps were ineffective in collecting larvae at the relatively high-current site, and channel nets were less efficient in collecting larvae at the low-current site. Use of only one of these sampling methods would clearly result in biased and inaccurate estimates of the spatial variation in larval abundance among locations that differ in current velocity. When selecting a larval sampling device, one must consider not only how well a particular taxon may be represented, but also the environmental conditions under which the device will be deployed.
    Keywords: Biology ; Ecology ; Fisheries
    Repository Name: AquaDocs
    Type: article , TRUE
    Format: application/pdf
    Format: application/pdf
    Format: 404-413
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  • 6
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    Integration of submersible transect data and high-resolution multibeam sonar imagery for a habitat-based groundfish assessment of Heceta Bank, Oregon (2021)
    In:  http://aquaticcommons.org/id/eprint/15247 | 403 | 2014-05-30 21:15:59 | 15247 | United States National Marine Fisheries Service
    Details
    Publication Date: 2021-07-05
    Description: In the face of dramatic declines in groundfish populations and a lack of sufficient stock assessment information, a need has arisen for new methods of assessing groundfish populations. We describe the integration of seafloor transect data gathered by a manned submersible with high-resolution sonar imagery to produce a habitat-based stock assessment system for groundfish. The data sets used inthis study were collected from Heceta Bank, Oregon, and were derived from 42 submersible dives (1988–90) and a multibeam sonar survey (1998). The submersible habitat survey investigated seafloor topography and groundfish abundance along 30-minute transects over six predetermined stations and found a statistical relationship between habitat variability and groundfish distribution and abundance. These transects were analyzed in a geographic information system (GIS) by using dynamic segmentation to display changes in habitat along the transects. We used the submersible data to extrapolate fish abundance within uniform habitat patches over broad areas of the bank by means of a habitat classification based on the sonar imagery. After applying a navigation correction to the submersible-based habitat segments, a good correlation with major boundaries on the backscatter and topographic boundaries on the imagery were apparent. Extrapolation of the extent of uniform habitats was made in the vicinity of the dive stations and a preliminary stock assessment of several species of demersal fish was calculated. Such a habitat-based approach will allow researchers to characterize marine communities over large areas of the seafloor.
    Keywords: Fisheries ; Management ; Oceanography
    Repository Name: AquaDocs
    Type: article , TRUE
    Format: application/pdf
    Format: application/pdf
    Format: 739-751
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