Density-dependent habitat use and growth of an estuarine fish

2012 ◽  
Vol 69 (11) ◽  
pp. 1734-1747 ◽  
Author(s):  
Nathan M. Bacheler ◽  
Jeffrey A. Buckel ◽  
Lee M. Paramore
Keyword(s):  
Habitat Use ◽  
Density Dependence ◽  
Growth Rates ◽  
Environmental Variability ◽  
Red Drum ◽  
Individual Growth ◽  
Estuarine Fish ◽  
Feedback Controls ◽  
Density Dependent ◽  
Spatial And Temporal Scales

Density dependence can stabilize or destabilize population size through negative or positive feedback controls operating over different spatial and temporal scales. While many species have been shown to exhibit density dependence, the topic has received little attention in estuaries where environmental variability and larval supply are often considered to be the primary drivers of population dynamics. We used multiple long-term, fishery-independent data sets and a unique modeling approach to test the hypothesis that juvenile red drum ( Sciaenops ocellatus ) exhibit density-dependent habitat use and growth rates in estuaries in North Carolina, USA. Age-1 red drum exhibited density-dependent habitat use after accounting for environmental and landscape variables, disproportionately increasing northward and coastward in the study area at high abundance. Apparent individual growth rates of age-0 and age-1 red drum were generally negatively related to the abundance of their own age classes, but evidence of density-dependent growth rates for age-2 red drum was weak to nonexistent. Changes in spatial distribution of red drum when overall abundance was high did not overcome density-dependent effects on individual growth rates. Thus, density-dependent effects have potential negative feedbacks on population growth in estuaries and should not be ignored in future theoretical or empirical estuarine studies.

Biology of Gadus morhua in Ogac Lake, a Landlocked Fiord on Baffin Island

1967 ◽  
Vol 24 (12) ◽  
pp. 2573-2594 ◽  
Author(s):  
David G. Patriquin
Keyword(s):  
Growth Rates ◽  
Gadus Morhua ◽  
Environmental Variability ◽  
Sea Urchins ◽  
High Growth ◽  
Baffin Island ◽  
Meristic Characters ◽  
Large Size ◽  
Fin Ray ◽  
High Length

Gadus morhua L. occurs in Ogac Lake, a salt, meromictic lake on Baffin Island that receives influxes of seawater only during the highest summer tides. Cod of the order of 10,000 of lengths 25 cm and greater and 500 of lengths greater than 60 cm were present. The size ranges for various ages far exceeded those of oceanic populations. Feeding conditions were poor, and sea urchins predominated in the diet. Large cod (greater than 50 cm) were highly cannibalistic, and it was estimated that they consume of the order of 3500 fish of 20–40 cm annually. Maturation occurred at the unusually large size of 85 cm in females, and at about 65 cm in males. Apparently many of the cod never reach these sizes. Spawning was from late May to early July in 1962, and initiation of spawning appeared to be related to light. The hatching of cod larvae coincided with the appearance of the nauplii of the dominant copepod in the lake. Egg size was highly variable and exhibited a curious bimodalism. Variation in vertebral and fin-ray counts was slight in spite of high environmental variability, and thus appears largely genetically controlled. Possibly the first inhabitants came from Greenland stocks, which have high growth rates similar to the faster growing cod in the lake, and similar high length at maturity. Meristic characters also suggest affinity with Greenland rather than Labrador cod. The hydrography of the area and the possibilities of larval drift or adult migration into the lake are discussed. Cannibalism must exert continuing selection for high growth rates, but very poor feeding conditions and hierarchial dominance effects probably prevent general attainment of high growth rates.

Geostatistically modeling stem size and increment in an old-growth forest

1994 ◽  
Vol 24 (7) ◽  
pp. 1354-1368 ◽  
Author(s):  
Franco Biondi ◽  
Donald E. Myers ◽  
Charles C. Avery
Keyword(s):  
Spatial Patterns ◽  
Growth Rates ◽  
Spatial Dependence ◽  
Basal Area ◽  
Tree Density ◽  
Individual Growth ◽  
Old Growth ◽  
Model Estimate ◽  
Stem Size ◽  
Old Growth Forest

Geostatistics provides tools to model, estimate, map, and eventually predict spatial patterns of tree size and growth. Variogram models and kriged maps were used to study spatial dependence of stem diameter (DBH), basal area (BA), and 10-year periodic basal area increment (BAI) in an old-growth forest stand. Temporal variation of spatial patterns was evaluated by fitting spatial stochastic models at 10-year intervals, from 1920 to 1990. The study area was a naturally seeded stand of southwestern ponderosa pine (Pinusponderosa Dougl. ex Laws. var. scopulorum) where total BA and tree density have steadily increased over the last decades. Our objective was to determine if increased stand density simply reduced individual growth rates or if it also altered spatial interactions among trees. Despite increased crowding, stem size maintained the same type of spatial dependence from 1920 to 1990. An isotropic Gaussian variogram was the model of choice to represent spatial dependence at all times. Stem size was spatially autocorrelated over distances no greater than 30 m, a measure of average patch diameter in this forest ecosystem. Because patch diameter remained constant through time, tree density increased by increasing the number of pine groups, not their horizontal dimension. Spatial dependence of stem size (DBH and BA) was always much greater and decreased less through time than that of stem increment (BAI). Spatial dependence of BAI was close to zero in the most recent decade, indicating that growth rates in 1980–1990 varied regardless of mutual tree position. Increased tree crowding corresponded not only to lower average and variance of individual growth rates, but also to reduced spatial dependence of BAI. Because growth variation was less affected by intertree distance with greater local crowding, prediction of individual growth rates benefits from information on horizontal stand structure only if tree density does not exceed threshold values. Simulation models and area estimates of tree performance in old-growth forests may be improved by including geostatistical components to summarize ecological spatial dependence.

Wintertime growth in Atlantic salmon under changing climate: the importance of ice cover for individual growth dynamics

2021 ◽  
Author(s):  
Laura Härkönen ◽  
Pauliina Louhi ◽  
Riina Huusko ◽  
Ari Huusko
Keyword(s):  
Climate Change ◽  
Atlantic Salmon ◽  
Growth Rates ◽  
Growth Dynamics ◽  
Ice Cover ◽  
Individual Growth ◽  
Late Winter ◽  
Dynamic Nature ◽  
Individual Level ◽  
Growth Variation

Understanding the dynamic nature of individual growth in stream-dwelling salmonids may help forecast consequences of climate change on northern fish populations. Here, we performed an experimental capture-mark-recapture study in Atlantic salmon to quantify factors influencing wintertime growth variation among juveniles under different scenarios for ice cover reduction. We applied multiple imputation to simulate missing size observations for unrecaptured fish, and to account for individual-level variation in growth rates. The salmon parr exhibited substantial body length shrinkage in early winter, suppressed growth through mid-winter, and increasing growth rates in late winter and particularly in spring. Unexpectedly, the presence of ice cover had no direct effects on wintertime growth. Instead, our results implied increasing energetic costs with reducing ice cover: individuals exposed to absent or shortened ice-covered period gained mass at a lowered rate in spring whereas the present, long ice-covered period was followed by rapid growth. This study emphasizes natural resilience of Atlantic salmon to wintertime environmental variation which may help the species to cope with the reductions in ice cover duration due to climate change.

scholarly journals Conspecific negative density dependence and why its study should not be abandoned

2020 ◽  
Author(s):  
Joseph A. LaManna ◽  
Scott A. Mangan ◽  
Jonathan A. Myers
Keyword(s):  
Density Dependence ◽  
Latitudinal Gradient ◽  
Null Model ◽  
Statistical Bias ◽  
Fitness Components ◽  
Density Dependent ◽  
Statistical Errors ◽  
Negative Density Dependence ◽  
Model Approach

AbstractRecent studies showing bias in the measurement of density dependence have the potential to sow confusion in the field of ecology. We provide clarity by elucidating key conceptual and statistical errors with the null-model approach used in Detto et al. (2019). We show that neither their null model nor a more biologically-appropriate null model reproduces differences in density-dependent recruitment between forests, indicating that the latitudinal gradient in negative density dependence is not an artefact of statistical bias. Finally, we suggest a path forward that combines observational comparisons of density dependence in multiple fitness components across localities with mechanistic and geographically-replicated experiments.

scholarly journals The Effect of Conspecific Density on Emergence ofLestes bipupillatusCalvert, 1909 (Odonata: Lestidae)

2014 ◽  
Vol 2014 ◽  
pp. 1-3 ◽  
Author(s):  
Ricardo Cardoso-Leite ◽  
Gabriel C. Vilardi ◽  
Rhainer Guillermo-Ferreira ◽  
Pitágoras C. Bispo
Keyword(s):  
Population Dynamics ◽  
Density Dependence ◽  
Social Environment ◽  
Growth Rates ◽  
High Density ◽  
Conspecific Density ◽  
Simulated Environments ◽  
The Social ◽  
Emergence Date

Conspecific density may influence adult recruitment and consequently population dynamics. Several studies have shown the density dependence of larvae growth rates in Odonata. However, few studies studied how conspecific density influence final instar larvae emergence date decisions. Considering that larvae may choose the date of emergence, the present study investigated if density affects larvae choice. For this, we reared eight final instar larvae in individual aquaria and other 24 larvae in aquaria with three larvae each. This way, we simulated environments with low and high larval densities. We then noted the days that larvae took to emerge and compared it between low and high density groups. The results showed that larvae seem to emerge earlier when in high densities (Mann-Whitney,U=10.000,P=0.03). These results support the hypothesis that damselfly last instar larvae may postpone or hasten emergence in response to the social environment and related constraints.

Do abiotic mechanisms determine interannual variability in length-at-age of juvenile Arcto-Norwegian cod?

2002 ◽  
Vol 59 (1) ◽  
pp. 57-65 ◽  
Author(s):  
Geir Ottersen ◽  
Kristin Helle ◽  
Bjarte Bogstad
Keyword(s):  
Growth Rates ◽  
Gadus Morhua ◽  
Barents Sea ◽  
Water Masses ◽  
Inverse Relation ◽  
Lower Growth ◽  
Density Dependent ◽  
The Barents Sea ◽  
The Mean ◽  
Dependent Growth

For the large Arcto-Norwegian stock of cod (Gadus morhua L.) in the Barents Sea, year-to-year variability in growth is well documented. Here three hypotheses for the observed inverse relation between abundance and the mean length-at-age of juveniles (ages 1–4) are suggested and evaluated. Based on comprehensive data, we conclude that year-to-year differences in length-at-age are mainly determined by density-independent mechanisms during the pelagic first half year of the fishes' life. Enhanced inflow from the southwest leads to an abundant cohort at the 0-group stage being distributed farther east into colder water masses, causing lower postsettlement growth rates. We can not reject density-dependent growth effects related to variability in food rations, but our data do not suggest this to be the main mechanism. Another hypothesis suggests that lower growth rates during periods of high abundance are a result of density-dependent mechanisms causing the geographic range of juveniles to extend eastwards into colder water masses. This is rejected mainly because year-to-year differences in mean length are established by age 2, which is too early for movements over large distances.

Sign in / Sign up

Export Citation Format

Share Document