scholarly journals Forage fish abundance is a predictor of timing of breeding and hatching brood size in a coastal seabird

2015 ◽  
Vol 519 ◽  
pp. 209-220 ◽  
Author(s):  
SH Lorentsen ◽  
T Anker-Nilssen ◽  
KE Erikstad ◽  
N Røv
Keyword(s):  
Brood Size ◽  
Fish Abundance ◽  
Forage Fish ◽  
Timing Of Breeding

scholarly journals Seabird‐induced natural mortality of forage fish varies with fish abundance: Evidence from five ecosystems

2020 ◽  
Author(s):  
Claire Saraux ◽  
William J. Sydeman ◽  
John F. Piatt ◽  
Tycho Anker‐Nilssen ◽  
Jonas Hentati‐Sundberg ◽  
...  
Keyword(s):  
Fish Abundance ◽  
Forage Fish ◽  
Natural Mortality

Towards a balanced presentation and objective interpretation of acoustic and trawl survey data, with specific reference to the eastern Scotian Shelf

2016 ◽  
Vol 73 (12) ◽  
pp. 1914-1921 ◽  
Author(s):  
J. Michael Jech ◽  
Ian H. McQuinn
Keyword(s):  
Atlantic Cod ◽  
Management Strategies ◽  
Pelagic Fish ◽  
Trophic Levels ◽  
Fish Abundance ◽  
Forage Fish ◽  
Specific Reference ◽  
Trawl Survey ◽  
Scotian Shelf ◽  
Eastern Canada

A debate has developed over the ecosystem consequences following the collapse of Atlantic cod throughout the coastal waters of eastern Canada. The explosive increase in pelagic fish abundance in scientific bottom-trawl catches on the eastern Scotian Shelf has been interpreted as being due to either (i) a “pelagic outburst” of forage fish abundance resulting from predator release or conversely (ii) a change in pelagic fish vertical distribution leading to a “suprabenthic habitat occupation” thereby increasing their availability to bottom trawls. These two interpretations have diametrically opposing ecological consequences and suggest different management strategies for these important forage fish species. We argue that an objective evaluation of the available evidence supports the hypothesis that the abundance of forage fish has not increased in response to the demise of cod and other top predators, and the reliance on a single sampling gear with low catchability has biased and will continue to bias the interpretation of demographic trends of pelagic fish populations. We advocate that multiple sampling technologies providing alternative perspectives are needed for the monitoring and management of the various trophic levels if we are to achieve a balanced and objective understanding of marine ecosystems.

Evaluating impacts of forage fish abundance on marine predators

2021 ◽  
Author(s):  
Christopher M. Free ◽  
Olaf P. Jensen ◽  
Ray Hilborn
Keyword(s):  
Fish Abundance ◽  
Forage Fish ◽  
Marine Predators

Community Ecology of Stream Fishes: Concepts, Approaches, and Techniques

2010 ◽  
Keyword(s):  
Brown Trout ◽  
Brook Trout ◽  
Fish Assemblages ◽  
Smallmouth Bass ◽  
Fish Abundance ◽  
Forage Fish ◽  
Data Sets ◽  
Biotic Factors ◽  
Habitat Factors ◽  
Habitat Variables

<em>Abstract</em>.—In regional survey studies of habitat and fish assemblages, potentially important biological interactions can be masked by strong gradients in habitat variables and associated collinearities among biological variables. We used structural equation modeling to compare the causal influences of local habitat and biotic factors on fish density in rivers and to determine the extent to which the set of sites chosen for analysis influenced their apparent importance. When all sites in our Michigan data set were used, spatial patterns in brook trout <em>Salvelinus fontinalis </em>biomass were 28 times more sensitive to habitat variables than brown trout <em>Salmo trutta </em>biomass. However, when the sample was restricted to trout streams, then brook trout biomass patterns were twice as sensitive to brown trout biomass as habitat variables. In a similar analysis for smallmouth bass <em>Micropterus dolomieu</em>, habitat factors had the strongest effects on fish densities when the analysis was based on all samples available. However, when the sample was limited to steams in which smallmouth bass actually occurred, direct effects of forage fish abundance and indirect effects of habitat via forage fish abundance were more prominent. In both the trout and smallmouth bass analyses, regional data sets (which included sites where the species of interest was absent) overemphasized the importance of habitat factors on fish abundance, but restricting the sample to sites having the species of interest elevated the importance of biotic factors. In reality, both habitat and biotic factors are important to these species, but the variance structure of the sample being analyzed had an overriding influence on the statistical importance of one versus the other. These findings help to resolve apparently conflicting results of previous studies assessing the relative influence of habitat and biotic factors on population abundance.

The impact of climate and cyclic food abundance on the timing of breeding and brood size in four boreal owl species

Oecologia ◽  
2010 ◽  
Vol 165 (2) ◽  
pp. 349-355 ◽  
Author(s):  
Aleksi Lehikoinen ◽  
Esa Ranta ◽  
Hannu Pietiäinen ◽  
Patrik Byholm ◽  
Pertti Saurola ◽  
...  
Keyword(s):  
Brood Size ◽  
Food Abundance ◽  
Timing Of Breeding ◽  
Boreal Owl ◽  
The Impact

The Effect of Drought on Duckling Survival of Maned Ducks

1989 ◽  
Vol 16 (4) ◽  
pp. 405 ◽  
Author(s):  
RT Kingsford
Keyword(s):  
Reproductive Success ◽  
Brood Size ◽  
Timing Of Breeding ◽  
Hatch Date ◽  
Seasonal Differences ◽  
Probability Of Survival ◽  
South Eastern ◽  
Duckling Survival ◽  
Eastern Australia ◽  
Brood Surveys

Regular brood surveys on a population of maned ducks, Chenonetta jubata, in south-eastern Australia provided information on the timing of breeding, brood sizes, duckling survival and production for this species. Over three years (1981-83), most breeding was during the spring, ducklings hatching between late August and late November. Some autumn (March-May) breeding also occurred. Timing of breeding appeared to be more closely related to the abundance of food than to rainfall alone. There were clear differences in reproductive success between the drought year of 1982 and the two years of similar weather, 1981 and 1983. Breeding began later in 1982, with a mean hatch date of 18 � 5.1 November, compared with 7 � 3.6 October in 1981 and 21 � 5.1 September in 1983. Broods hatched over 43 days in 1982 compared with 69 days in 1981 and 101 days in 1983. Also, duckling survival was lowest in 1982, with about a 20% probability of survival to fledging compared with 89% in 1981 and 82% in 1983. Only six broods were found in 1982 compared with 33 in 1981 and 30 in 1983. An estimated 158 and 176 ducklings survived to fledging compared with seven in 1982. Brood sizes at hatching did not show the same clear annual differences. In 1981 and 1983 there were seasonal differences in brood size at hatching. Broods were smaller late in the season (4.1) compared with early (7.2) and mid-season (7.2). Broods were also larger in 1983 (7.2) than in 1981 (5.4). Brood size at hatching in 1982 was 6.0.

Sign in / Sign up

Export Citation Format

Share Document