Food availability and initial relative abundance determine the outcome of interspecific competition between two different-sized cladocerans

2016 ◽  
Vol 101 (3-4) ◽  
pp. 105-112 ◽  
Author(s):  
Rui Chen ◽  
Hengxing Tang ◽  
Feixi Zhao ◽  
Yingyuan Wu ◽  
Yuan Huang ◽  
...  
Keyword(s):  
Interspecific Competition ◽  
Food Availability ◽  
Relative Abundance

A stock survey technique using the time to capture individual fish on longlines

1995 ◽  
Vol 52 (2) ◽  
pp. 260-267 ◽  
Author(s):  
David A. Somerton ◽  
Bert S. Kikkawa
Keyword(s):  
Interspecific Competition ◽  
Relative Abundance ◽  
Fish Abundance ◽  
Fish Populations ◽  
Small Fish ◽  
Target Species ◽  
Time Data ◽  
New Approach ◽  
Survey Technique ◽  
Nontarget Species

Longline catches per unit of effort (CPUE) from research surveys are often assumed to vary in proportion to fish abundance. This assumption, however, may be invalid if the abundance of the target species is high enough to saturate the gear or if the abundance of nontarget species is high enough to exclude the target species from capture. We examine a new approach to surveying fish populations with longlines that is based on time-to-capture data measured with small, fish-activated timing devices attached to every hook. A new measure of relative abundance, λ, is developed that is immune to the effects of gear saturation and interspecific competition for hooks. Two estimators of λ are compared by using capture-time data collected during summer 1987–1991 for pelagic armorhead (Pseudopentaceros wheeleri). Both estimators are shown to be unbiased if the underlying assumptions are true and fairly robust to the observed departures from these assumptions.

Disponibilidad y uso de recursos tróficos por Lacerta schreiberi y Podarcis bocagei en simpatría en una localidad de la Cordillera Cantábrica, España

1990 ◽  
Vol 11 (3) ◽  
pp. 237-246 ◽  
Author(s):  
Alfredo Salvador ◽  
José F. Domínguez
Keyword(s):  
Food Availability ◽  
Relative Abundance ◽  
Diet Composition ◽  
Cantabrian Mountains ◽  
Sympatric Populations ◽  
Trophic Resources ◽  
Podarcis Bocagei

AbstractFood availability and diet composition were examined in sympatric populations of Lacerta schreiberi and Podarcis bocagei at a locality in the Cantabrian mountains (province of León, Spain). Neither species uses trophic resources in proportion to their relative abundance. Extensive overlap in diet composition has been found between P. bocagei and juvenile L. schreiberi. Although both species feed mainly on spiders, juvenile L. schreiberi eat the most abundant and P. bocagei select larger prey sizes. Subadult and adult L. schreiberi select beetles and grasshoppers.

Performance of Domestic, Hybrid, and Wild Strains of Brook Trout, Salvelinus fontinalis, after Stocking: the Impact of Intra- and Interspecific Competition

1990 ◽  
Vol 47 (12) ◽  
pp. 2278-2284 ◽  
Author(s):  
Stephanie Lachance ◽  
Pierre Magnan
Keyword(s):  
Interspecific Competition ◽  
Relative Abundance ◽  
Brook Trout ◽  
Salvelinus Fontinalis ◽  
White Sucker ◽  
Catostomus Commersoni ◽  
Oligotrophic Lakes ◽  
Wild Strains ◽  
The Impact ◽  
Response Variables

Wild and hybrid strains of brook trout, Salvelinus fontinalis, showed better rates of recovery (by angling) and yield (kilograms of fish recovered per kilogram planted) than a domestic strain, during the 2 yr following planting, in six small oligotrophic lakes of the Laurentian Shield. Native brook trout and white sucker, Catostomus commersoni, had a significant impact on planted brook trout. Recovery, percent of increment in weight and yield of each planted strain were inversely correlated with (1) the relative abundance of native brook trout, and (2) the occurrence of white sucker, supporting hypotheses of intra- and interspecific competition. Furthermore, the response variables were also inversely correlated with the number of potential competitors, indicating that the impact of native brook trout and white sucker was additive. The recovery in number of planted trout (both years and all strains) was approximately four times higher in lakes with effectively no competitors than in lakes containing both white sucker and native brook trout; the increase in weight was nearly three times higher, and the yield was more than nine times higher. The performances of planted fish were intermediate in the lake containing only native brook trout as competitor.

Modelling the abundance and productivity distribution to understand the habitat–species relationship: the guanaco (Lama guanicoe) case study

2020 ◽  
Vol 47 (6) ◽  
pp. 448
Author(s):  
Celina E. Flores ◽  
Laura M. Bellis ◽  
Schiavini Adrián
Keyword(s):  
Interspecific Competition ◽  
Breeding Season ◽  
Food Availability ◽  
Geographic Location ◽  
Distribution Patterns ◽  
Species Relationship ◽  
Productivity Distribution ◽  
Forage Availability ◽  
Feral Dogs ◽  
Family Groups

Abstract ContextThe conservation of large wild herbivores presents a challenge posed by the fact that their broad habitat requirements overlap with various human activities. Elucidating the factors that explain their distribution patterns provides us with a better understanding of habitat–species relationships and facilitates the design of effective management policies. AimsIdentify the natural (forage availability, weather) and anthropogenic (hunting, interspecific competition) factors that explain the abundance and productivity distribution of the guanaco. Estimate guanaco abundance and productivity and describe their distribution. MethodsWe estimated the abundance and productivity of guanaco by using aerial surveys during the breeding and non-breeding season of two consecutive years, following the strip-transect methodology; we then modelled these as a function of environmental factors by means of density surface models. Key resultsThe highest abundance and productivity of guanaco occurred mostly where mesic grassland was dominant. Guanaco abundance presented three hotspots on the basis of geographic location, and family groups were more productive at low to intermediate livestock level. Abundance was significantly higher in the breeding season for both years (5614 and 14092 individuals) than in the non-breeding season (2922 and 6926 individuals), and it was higher in 2015 than in 2014. Productivity was higher in 2015 than in 2014 (0.54 and 0.46 calves per adult respectively). ConclusionsGuanaco responded to forage availability, occupying zones with low to intermediate food availability in the breeding season, and those with the highest availability in the non-breeding season. This could be due to interspecific competition between livestock and guanaco family groups. We propose that the overall guanaco response could also be explained by social structure or by unassessed factors such as predation risk by feral dogs. ImplicationsThe guanaco could compensate for the use of habitats with a lower food availability during the breeding season by using better-quality habitats during the non-breeding season.

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