scholarly journals A hierarchical model to estimate the abundance and biomass of salmonids by using removal sampling and biometric data from multiple locations

2010 ◽  
Vol 67 (12) ◽  
pp. 2032-2044 ◽  
Author(s):  
Philippe Ruiz ◽  
Christophe Laplanche
Keyword(s):  
Spatial Variability ◽  
Hierarchical Model ◽  
Salmo Trutta ◽  
Credible Interval ◽  
Fish Length ◽  
Biometric Data ◽  
Bayesian Hierarchical ◽  
Fish Model ◽  
Brown Trout Salmo Trutta ◽  
Removal Sampling

We present a Bayesian hierarchical model to estimate the abundance and the biomass of brown trout ( Salmo trutta fario ) by using removal sampling and biometric data collected at several stream sections. The model accounts for (i) variability of the abundance with fish length (as a distribution mixture), (ii) spatial variability of the abundance, (iii) variability of the catchability with fish length (as a logit regression model), (iv) spatial variability of the catchability, and (v) residual variability of the catchability with fish. Model measured variables are the areas of the stream sections as well as the length and the weight of the caught fish. We first test the model by using a simulated dataset before using a 3-location, 2-removal sampling dataset collected in the field. Fifteen model alternatives are compared with an index of complexity and fit by using the field dataset. The selected model accounts for variability of the abundance with fish length and stream section and variability of the catchability with fish length. By using the selected model, 95% credible interval estimates of the abundances at the three stream sections are (0.46,0.59), (0.90,1.07), and (0.56,0.69) fish/m2. Respective biomass estimates are (9.68, 13.58), (17.22, 22.71), and (12.69, 17.31) g/m2.

scholarly journals Study on the fecundity of Salmo trutta fario (Brown trout) in Kashmir

2012 ◽  
Vol 4 (1) ◽  
Author(s):  
Nusrat Rasool ◽  
Ulfat Jan
Keyword(s):  
Brown Trout ◽  
Salmo Trutta ◽  
Mean Value ◽  
Fish Length ◽  
Gonad Somatic Index ◽  
Brown Trout Salmo Trutta ◽  
Total Fish ◽  
The Right ◽  
Somatic Index ◽  
Salmo Trutta Fario

The study has been carried in the year 2004 and describes fecundity, spawning season and sex ratio of brown trout, Salmo trutta fario. A total of 121 brown trout (67 males and 54 females) were captured by angling. Gonad somatic index (GSI) confirmed that spawning lasted from October to December. The left ovary, with some exceptions, was found to be longer and heavier producing more eggs than the right one. The absolute fecundity of sampled population varied from 527 to 2445 and the relative fecundity had a mean value of 2.56. Fecundity was positively co-related with the total fish length (r=0.865), fish weight (r=0.9426) ovary weight (r=0.952) and ovary length (r=0.845).

scholarly journals A Bayesian hierarchical model of postlarval delta smelt entrainment: integrating transport, length composition, and sampling efficiency in estimates of loss

2020 ◽  
Vol 77 (5) ◽  
pp. 789-813
Author(s):  
William E. Smith ◽  
Ken B. Newman ◽  
Lara Mitchell
Keyword(s):  
Hierarchical Model ◽  
Hierarchical Modeling ◽  
Bayesian Hierarchical Model ◽  
Model Parameters ◽  
Fish Length ◽  
Sampling Efficiency ◽  
Multiple Sources ◽  
Hydrodynamic Models ◽  
Delta Smelt ◽  
Bayesian Hierarchical

Hydrodynamic models have been used to estimate rates of ichthyoplankton transport across marine and estuarine environments and subsequent geographic isolation of a portion of the population (i.e., entrainment). Combining simulated data from hydrodynamic models with data from fish populations can provide more information, including estimates of regional abundance. Entrainment of postlarval delta smelt (Hypomesus transpacificus), a threatened species endemic to California’s Sacramento–San Joaquin Delta, caused by water export operations, was modeled using a Bayesian hierarchical model. The model was fit using data spanning years 1995–2015 from multiple sources: hydrodynamic particle tracking, fish length composition, mark–recapture, and count data from entrainment monitoring. Estimates of the entrainment of postlarval delta smelt ranged from 10 (SD = 23) in May 2006 to 561 791 (SD = 246 423) in May 2002. A simulation study indicated that all model parameters were estimable, but errors in transport data led to biased estimates of entrainment. Using only single data sources rather than integration through hierarchical modeling would have underestimated uncertainty in entrainment estimates or resulted in bias if transport, survival, or sampling efficiency were unaccounted for.

Estimating riverine fish population size from single- and multiple-pass removal sampling using a hierarchical model

2002 ◽  
Vol 59 (4) ◽  
pp. 695-706 ◽  
Author(s):  
Robin J Wyatt
Keyword(s):  
Population Size ◽  
Hierarchical Model ◽  
Bayesian Approach ◽  
Salmo Trutta ◽  
Target Area ◽  
Single Pass ◽  
Multiple Pass ◽  
Individual Site ◽  
Removal Sampling ◽  
Riverine Fish

A hierarchical model is described for estimating population size from single- and multiple-pass removal sampling. The model is appropriate for two-stage sampling schemes, typified by surveys of riverine fish populations, in which multiple sites are surveyed, but a low number of passes are undertaken at each site. The model estimates the average population size within the target area from the raw catch data, and thus allows for differences in the sampling procedure at each site, such as including single-pass sampling. The model also uses the data from all sites to estimate the population size at each individual site. This results in generally improved precision for multiple-pass sites and provides comparable estimates from single-pass sites. A Bayesian approach is described for estimating the parameters of the hierarchical model using sampling importance resampling (SIR). An empirical Bayesian approach, which ignores prior uncertainty but is simpler to implement, is also described. Application of the hierarchical model is illustrated with electrofishing data for 0+ trout (Salmo trutta) in the River Inny, U.K.

scholarly journals Modelling the factors influencing ontogenetic dietary shifts in stream-dwelling brown trout (Salmo trutta)

2018 ◽  
Vol 75 (4) ◽  
pp. 590-599 ◽  
Author(s):  
Javier Sánchez-Hernández ◽  
Fernando Cobo
Keyword(s):  
Body Length ◽  
Brown Trout ◽  
Salmo Trutta ◽  
Prey Availability ◽  
The Body ◽  
Habitat Characteristics ◽  
Water Current ◽  
Fish Length ◽  
Water Current Velocity ◽  
Brown Trout Salmo Trutta

Biotic and abiotic variables shape ontogenetic trajectories of animals. This study modelled (i) the body length related timing of the ontogenetic switch from aquatic to surface prey and (ii) the impacts of habitat characteristics, prey availability, and fish densities on the relative contribution of surface prey to the overall diet of native brown trout (Salmo trutta). We used individual-based models of dietary data for 170 fish (length range 48–343 mm). There was a high degree of individual variation in the use of surface prey, but logistic regression suggested that the shift from aquatic to surface prey was established at a body length of 81 mm (range 36–127 mm). Results of linear mixed-effects models highlighted the importance of fish length, benthic invertebrates, brown trout density, and water current velocity to the switch to surface prey by riverine brown trout, with fish length being the most influential variable. Our study provides evidence of the importance of ontogeny (intrinsic features of individuals linked to fish length) and individual differences in feeding behaviour to understand water-column use for feeding by stream-dwelling salmonids.

scholarly journals Territorial and foraging behaviour of juvenile Mediterranean trout under changing conditions of food and competitors

2016 ◽  
Vol 73 (6) ◽  
pp. 990-998 ◽  
Author(s):  
Graciela G. Nicola ◽  
Daniel Ayllón ◽  
Benigno Elvira ◽  
Ana Almodóvar
Keyword(s):  
Salmo Trutta ◽  
Global Analysis ◽  
Food Abundance ◽  
Territory Size ◽  
Fish Length ◽  
Critical Periods ◽  
Two Factors ◽  
Feeding Regimes ◽  
Brown Trout Salmo Trutta ◽  
Mediterranean Trout

Territoriality is probably the most important ecological mechanism regulating densities in stream-living salmonids. Body size is typically regarded as the best predictor of territory size, but food abundance and competitor density may be key driving factors. However, a global analysis of literature data showed no clear patterns on the relative causal role of those factors on determining territory size in juvenile salmonids. Thus, in a factorial experiment, we estimated to what extent simultaneous variations of fish size, competitor density, and food abundance affected the size of foraging and defended areas of Mediterranean brown trout (Salmo trutta). In contrast with former studies, we found that foraging areas were larger than defended territories. Foraging and territorial behaviour changed significantly under varying density and feeding regimes. Foraging areas decreased with increasing competitor density and food availability, and there was a strong interaction between these two factors. Defended territories decreased with increasing density, irrespective of food abundance. Although our findings showed a significant allometric relationship between fish length and territory size, the data contained much unexplained variability. Our findings suggest that defended areas are relatively fixed for a given trout length. However, at extremely high population densities, defended areas decreased. Thus, under extreme competition, such as during critical periods right after emergence, trout may subdivide available habitat and thereby moderate density declines.

Timing of Sea-Run Brown Trout (Salmo trutta) Smolt Migration: Effects of Climatic Variation

1993 ◽  
Vol 50 (6) ◽  
pp. 1132-1136 ◽  
Author(s):  
Torgny Bohlin ◽  
Claes Dellefors ◽  
Ulo Faremo
Keyword(s):  
Brown Trout ◽  
Salmo Trutta ◽  
Close Agreement ◽  
Climatic Variation ◽  
Fish Length ◽  
Degree Days ◽  
Annual Fish ◽  
Small Stream ◽  
Brown Trout Salmo Trutta ◽  
Parameter Values

By trapping seaward migrating smolts of brown trout (Salmo trutta), we analyzed the timing of the run in a small stream in southwestern Sweden (58°N) during 1984–90 in relation to environmental factors. Ninety percent of the smolts were captured during a period of 28.7 d (SD 5.9), with median time ranging from April 26 to May 17. Using polynomial multiple regression, we found a positive relationship between the probability of migration per day and the number of degree-days, change in water level, temperature change during the preceding week, and mean annual fish length. Forty-seven percent of the variation was explained. The predicted probabilities were used to calculate the population fraction migrating per day for the seasons 1984–90. There was a close agreement between the observed and expected daily fraction of migrants. The model, with parameter values based on the observations from 1984–90, was also used to predict the daily migration in 1991. The result indicated that the model accurately predicts the smolt run (R2 = 0.40).

Sign in / Sign up

Export Citation Format

Share Document