首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
Bayesian hierarchical models were developed to estimate the growth parameters of northern abalone, Haliotis kamtschatkana, using tag-recapture data with a mixture of single and multiple recaptures. Individual variability in the growth parameters L and k of the von Bertalanffy model was incorporated in the analyses. The models developed fit the data well based on the Bayesian p-values. Variability in L for individuals was high relative to the variability in L for the population, and variability in k for individuals was about the same as the variability in k for the population. Simulations showed that estimates of the growth parameters were accurate (relative biases <5%), when variability in both L and k or just in L was accounted for. The “true” values of the parameters, L and k, were contained in the estimated 95% credibility intervals in 90–94 out of 100 simulation runs on 100 simulated data sets. Overall, allowing for variability for both L and k resulted in moderately more accurate estimates than allowing for just L. On the contrary, estimates were unreliable when variability in just k was considered. Using the WinBUGS software program, the calculation procedure was rather simple irrespective of which growth parameter was modeled with variability.  相似文献   

2.
《Fisheries Research》2006,82(2-3):229-235
Model selection based on information theory is a relatively new paradigm in biological sciences with several advantages over the classical approaches. The aim of the present study was to apply information theory in the area of modelling fish growth and to show how model selection uncertainty may be taken into account when estimating growth parameters. The methodology was applied for length–age data of four species of fish, taken from the literature. Five-candidate models were fitted to each dataset: von Bertalanffy growth model (VBGM), generalized VBGM, Gompertz growth model, Schnute–Richards growth model, and logistic. In each case, the ‘best’ model was selected by minimizing the small-sample, bias-corrected form of the Akaike information criterion (AIC). To quantify the plausibility of each model, given the data and the set of five models, the ‘Akaike weight’ wi of each model was calculated. The average model was estimated for each case based on wi. Following a multi-model inference (MMI) approach, the model-averaged asymptotic length L¯ for each species was estimated, using all five models, by model-averaging estimations of L and weighting the prediction of each model by wi. In the examples of this study, model selection uncertainty caused a magnification of the standard error of the asymptotic length of the best model (up to 3.9 times) and thus in all four cases estimating L from just the best model would have caused overestimation of precision of the asymptotic length. The VBGM, when used for inference, without being the best model, could cause biased point estimation and false evaluation of precision. Model selection uncertainty should not be ignored even if VBGM is the best model. Multi-model inference by model-averaging, based on Akaike weights, is recommended for making robust parameter estimations and for dealing with uncertainty in model selection.  相似文献   

3.
From 2003 through 2006, 18,180 big skate (Raja binoculata) were tagged in three regions in British Columbia, Canada: northern Hecate Strait, Queen Charlotte Sound and the west coast of Vancouver Island. To date, this is the largest tagging program conducted for skates or rays worldwide. As of December 31, 2008, 7% of the tagged fish (n = 1238) have been recaptured through the commercial fisheries. Generally, 75% of the recaptured fish were recaptured within 21 km of the tagging location. Long-range movements (up to 2340 km) were undertaken by a small percentage (1.5%) of the recaptured fish. Tagged big skate were recaptured in waters off of Oregon, Washington, throughout the Gulf of Alaska and the Bering Sea. The majority of big skate recaptured outside of Canadian waters were female (83%, n = 15), of which 80% (n = 12) were likely immature at release. Three methods of estimating growth parameters were employed and produced varying results. The Gulland and Holt method was not able to produce growth parameter estimates. The GROTAG method for combined sexes produced von Bertalanffy growth curve parameters L (294.7 cm), K (0.05) and t0 (?1.44) that were similar to published estimates for British Columbia big skates. The von Bertalanffy growth curve parameters produced by Fabens method for combined sexes were L = 168.6 cm, K = 0.16 and t0 = ?0.81.  相似文献   

4.
An earlier cohort analysis using catch-at-length data (for the period May 1979–April 1980) on the stock of Osteochilus hasselti C. & V. computes statistics on: (1) the total stock at the start of the cohort (N = 22.7 × 105) (these stock numbers decrease progressively at successive lengths, in a steady state and assuming constant natural mortality rate, M = 2.1); (2) catch numbers in a cohort totalling 780 940 individuals; (3) the exploitation rate of the cohort of E = 0.34, suggesting moderate exploitation of the species at Bukit Merah Reservoir, Malaysia.However, the validity of cohort analysis on a species exploited at a very early age depends on the input value of the variables natural mortality rate (M), fishing mortality rate of terminal largest fish (Fter), and growth parameters (L, K). Because of the methodological difficulties in estimation and verification of M, Fter and K values of O. hasselti, a range of values of input variables is adopted for comparison. The effect of the variability of M values (0.5, 1.0, 1.5 and 2.5) on the computation results of smaller size-class fishes NL is significantly different from that based on M = 2.1, showing a much lower population size.The variability of input values of Fter (range 0.5–2.5) and K (0.28–2.62) is tested on their effects on the population size of recruits. The combined effect of M and K in the relationship of MK ranging from 0.8 to 2.5 is varied to decide the possible values of K. In general, the different input values of M, Fter and K result in lower estimates of the population size of recruits, Nr This is about 28% lower than Nr = 22.7 × 105 when M = Fter = 2.1 and K = 1.15. With an inherent computational bias, the population size of Nr = 22.7 × 105 is probably an under-estimate, but it is both reasonable and biologically possible for O. hasselti at Bukit Merah Reservoir, Malaysia, since the input variables are generated from representative length composition data of commercial catches and tagging data.  相似文献   

5.
We examined growth in length of fluvial bull trout (Salvelinus confluentus) in the Walla Walla River Basin, Washington and Oregon. Our objectives were to quantify individual variability in growth; examine growth within and among years, life history forms, life stages and sexes; and estimate von Bertalanffy growth parameters. Individual variability was evaluated by modelling asymptotic length (L) and the growth coefficient (k) as random variables. All models were fit with Bayesian methods and were evaluated for fit by the deviance information criterion. By incorporating individual variability, population‐level estimates of L and k appeared appropriate and estimated growth trajectories for specific bull trout fit individual observed patterns in growth. Growth trajectories and positive correlation between individual estimates of L and k suggest that some individuals grow at a faster rate and reach a larger maximum size than other individuals and those differences are maintained throughout life. Selected models suggest that fluvial migrants have higher estimates of L and k than residents, but there were only slight differences in parameter estimates among migrants from two adjacent spawning populations in the Walla Walla River Basin, as well as between males and females. Growth rates increased for fluvial migrants after subadult emigration. Individual variability in growth is consistent with the life history diversity assumed essential for bull trout population persistence. Quantifying this variability is important for modelling population dynamics and viability to conserve this threatened species.  相似文献   

6.
Three approaches for multivariate analysis of fish growth in aquaculture experiments with Nile tilapia (Oreochromis niloticus niloticus L.) based on the von Bertalanffy growth curve are presented and compared. The approaches are: an extended Gulland‐and‐Holt (GH) plot, a forced extended GH plot and a multilinear regression analysis for the growth parameter K. All three models provide valuable insight into the major environmental factors influencing the daily growth rate and explain 28–46% of the variance of the observed daily growth rate of the used data set. For all three methods, the modelled parameter is significantly related to the net yield of Nile tilapia and can, therefore, be used for the predictive modelling of management scenarios. The extended GH plot loads the influence of environmental parameters upon L, while the forced extended GH plot and Direct fitting of K load the influence on the growth parameter K. The latter is more in the tradition of aquaculture research. But the forced extended GH plot and Direct fitting of K can only be applied if L of the cultured species is known, as the selected L influences the variance in the regression variables.  相似文献   

7.
Abstract Estimates of the growth parameters (L and K), mortality coefficients (Z, M and F) and exploitation rate (E) for the blackspot snapper, Lutjanus fulviflamma (Forsskål) from the Mafia Island Marine Park (MIMP) and adjacent intensively fished areas in Tanzania were determined. Sectioned otoliths showed that L. fulviflamma in the MIMP attained a maximum age of 18 years, with a high proportion of fish between 6 and 10 years old. The maximum age was 8 years in the intensively fished areas, with a preponderance of 2‐ and 4‐year‐old fish. The size structures of the populations in the MIMP and that in the intensively fished areas were markedly different, with the MIMP fish averaging (±SE) 211.4 ± 0.38 mm TL, but 154.6 ± 0.32 mm TL in the intensively fished areas. The von Bertalanffy growth parameters were L = 290.3 mm TL, K = 0.15 year?1 and t0 = ?2.7 years. There was no significant difference in growth between the four populations (L: F‐stat = 0.14, P = 1.000, and K: F‐stat = 0.26, P = 0.992). Total mortality was 0.55 and 1.64 year?1 in the MIMP and intensively fished areas, respectively, natural mortality 0.27 year?1 and fishing mortality 0.18 and 1.37 year?1 in the MIMP and intensively fished areas, respectively. The exploitation rate was 0.51 and 0.84 in the MIMP and intensively fished areas, respectively. The artisanal seine net fishery is directed mainly at younger fish in the intensively fished areas resulting in growth overfishing. The protracted life span, the slow growth and natural mortality rates imply that L. fulviflamma is vulnerable to overfishing and that the protection provided by the park, although limited, is vital for sustaining the fishery at Mafia Island.  相似文献   

8.
《Fisheries Research》1988,6(4):363-378
Growth and mortality of adult Strombus gigas L. was studied in a population offshore of La Parguera, Puerto Rico. Adult queen conchs do not grow in shell length, but only in shell thickness. Growth in thickness of the flared shell-lip was measured during a 2-year mark-recapture study and modelled using the von Bertalanffy growth function. Model parameters were K=0.3706 year−1 and L (asymptotic lip-thickness) =54.9 mm; the third von Bertalanffy parameter, t0, cannot be obtained from mark-recapture data alone. Growth in tissue, meat and shell weights of adults were determined using the von Bertalanffy growth function in conjunction with regression equations for weights versus shell length and/or lip thickness. Total instantaneous mortality in adults, determined using von Bertalanffy parameters and lip-thickness frequency analysis, was 1.66 year−1. Subtracting a previous estimate of fishing mortality (F=1.14 year−1) yielded a natural mortality (M) of 0.52 year−1. Given an average age at maturation, defined by the formation of the flared shell-lip, of 3.2 years, the age of first reproduction was estimated at 3.6 years, but could be as much as 4 years.  相似文献   

9.
A 4‐year study (May 1997–December 2000) of the reproductive biology of pink dentex Dentex gibbosus (Rafinesque) from the Adriatic Sea revealed that this species is a rudimentary hermaphrodite. The smallest mature males and females captured were 38.70 cm in total length (TL) and 39.80 cm in total length (TL) respectively. The von Bertalanffy growth parameters estimated for the entire population were: L=107.24, K=0.12 and t0=−0.90. Fifty per cent of the population were sexually mature at 41.50 cm TL, while 100% of the specimens were sexually mature at 57.00 cm TL. Both monthly gonadosomatic index and macroscopically determined gonad stages strongly indicate that the pink dentex from the Adriatic Sea spawn partially in August, September and October. The mean value of absolute fecundity (F) was 1672 × 106 eggs. The results of great fertility of the pink dentex, partial spawning and relatively late sexual maturation suggest that the pink dentex has a high potential for commercial culture.  相似文献   

10.
Juvenile red drum (Sciaenops ocellatus) were cultured at 25°C on a variety of diets and blood sampled over eight weeks to examine the relationship between growth and plasma thyroid hormone levels. Maximum growth rates were achieved on formulated experimental diets and a simulated natural shrimp diet. Associated with these maximal rates was a significant increase in triidothyronine (T3), but no consistent change in thyroxine (T4). Reduced rations of diets resulted in low growth rates associated with significantly lowered levels of T3 but not T4. To determine whether weight gain could be increased by application of exogeneous hormone, diets were supplemented with T3 or T4 at 2, 10, and 50 mg hormone/kg diet. Significantly elevated T3 was induced by supplementation with 10 and 50 mg T3/kg diet, although there were no indications of an anabolic effect of T3 incorporation, and 50 mg T3/kg diet was in fact associated with decreased weight gain. Incorporation of T4 into diets had no effect on growth or T3, and had effects on T4 which were small and inconsistent, indicating that T4 may not be effectively absorbed from the gut. No difference was found in response to hormone feeding between low (6 ppt) or high (35 ppt) water salinity. T3 levels thus appear to closely parallel growth in fish on unsupplemented diets, whereas T4 which were small and manipulation. Supplementation with T3 is not an effective means of stimulating growth in red drum fed optimum diets. Whereas thyroid hormones may function to regulate intermediary metabolism in red drum, elevated endogenous thyroid hormone levels appear adequate to supply tissue needs during juvenile growth in culture.  相似文献   

11.
Britton JR, Harper DM, Oyugi DO. Is the fast growth of an equatorial Micropterus salmoides population explained by high water temperature? Ecology of Freshwater Fish 2010: 19: 228–238. © 2010 John Wiley & Sons A/S Abstract – Marginal increment analysis of scales collected from the introduced Micropterus salmoides population of Lake Naivasha, Kenya revealed the formation of an annual growth check, validating their use to age individual fish. Subsequent analysis of scales from 372 fish collected between 2002 and 2009 revealed individuals were very fast growing compared with native populations in North America and other introduced populations in Europe, South America, Africa and Asia. This was likely to be as a result of the water temperatures in Lake Naivasha exceeding 20 °C throughout the year. This was corroborated by a meta‐analysis of the growth parameters asymptotic length L and growth coefficient K from across their geographical range that revealed variance was explained by differences in mean annual air temperatures. At a break point of approximately 10 °C, there was a shift to reduced L and increased K, suggesting a temperature driven trade‐off between growth rate and ultimate length. When adjusted for temperature and weighted for sample size, there were significant differences between the growth parameters of the North American and introduced populations, suggesting that other abiotic and biotic variables were also important determinants of the growth of individuals between the two ranges.  相似文献   

12.
Introduced fishes can develop invasive populations that impact native species and ecosystems. Understanding the population ecology of introduced species in their extended ranges and how this compares to their native ranges is therefore important for informing their management. Here, the age and somatic growth rates of the piscivorous freshwater fish pikeperch Sander lucioperca were analysed across their invasive and native ranges to determine their spatial patterns and drivers. Analyses were initially completed in their invaded range in central and western England. Populations varied spatially in their growth rates; being slowest for a population in a narrow and shallow canal and fastest in a large, impounded lowland river. A meta‐analysis of parameters of the von Bertalanffy growth model then revealed that across their native and invasive ranges, their theoretical ultimate lengths (L) and growth coefficients (K) were significantly related to latitude, but not longitude. Their relationships with latitude were nonlinear, with higher values of L and lower values of K being evident towards their northerly and southerly range limits. Faster growth rates were evident in the middle of their range (45 to 55°N), suggesting temperatures here were most optimal for growth, but were in a trade‐off with reduced ultimate lengths. These spatial patterns suggest that whilst introduced S. lucioperca can colonise new waters across a wide area, the expression of their life‐history traits will vary spatially, with potential implications for how invasive populations establish and integrate into native fish communities.  相似文献   

13.
Abstract Temperature and oxygen gradients exist in nearly every water body, but anthropogenic activities can subject fish to rapid changes in these important environmental variables. These rapid changes in temperature and oxygen (generally referred to as temperature or oxygen shock) may have sub‐lethal consequences depending upon the magnitude and the fish species. This study quantified physiological changes in largemouth bass, Micropterus salmoides (Lacepède), exposed to two levels of heat and cold shocks and to two levels of hypoxic and hyperoxic shocks. Following a cold shock from 20 °C to 8 °C, plasma cortisol and glucose increased after 1 h and lactate dehydrogenase activity increased after 6 h. Plasma glucose and K+ concentrations increased 1 h after a heat shock from 20 °C to 32 °C but not after 6 h. Bass subjected to a hypoxic shock from 8 to 2 mg O2 L?1 showed decreased plasma K+ and increased plasma glucose and white muscle lactate. No changes in physiological parameters were observed in bass subjected up to 18 mg O2 L?1 hyperoxia. Results from this study suggest that largemouth bass can tolerate a wide range of temperature and oxygen shocks, but temperature decreases of 20 to 8 °C and hypoxia as low as 4 mg O2 L?1 should be avoided to minimise physiological perturbations.  相似文献   

14.
The natural mortality of exploited fish populations is often assumed to be a species‐specific constant independent of body size. This assumption has important implications for size‐based fish population models and for predicting the outcome of size‐dependent fisheries management measures such as mesh‐size regulations. To test the assumption, we critically review the empirical estimates of the natural mortality, M (year?1), of marine and brackish water fish stocks and model them as a function of von Bertalanffy growth parameters, L (cm) and K (year?1), temperature (Kelvin) and length, L (cm). Using the Arrhenius equation to describe the relationship between M and temperature, we find M to be significantly related to length, L and K, but not to temperature (R2 = 0.62, P < 0.0001, n = 168). Temperature and K are significantly correlated and when K is removed from the model the temperature term becomes significant, but the resulting model explains less of the total variance (R2 = 0.42, P < 0.0001, n = 168). The relationships between M, L, L, K and temperature are shown to be in general accordance with previous theoretical and empirical investigations. We conclude that natural mortality is significantly related to length and growth characteristics and recommend to use the empirical formula: ln(M) = 0.55 ? 1.61ln(L) + 1.44ln(L) + ln(K), for estimating the natural mortality of marine and brackish water fish.  相似文献   

15.
Genetic effects on cold‐stress tolerance were assessed for red drum (Sciaenops ocellatus), an economically important sciaenid fish in the southern USA. Thirty‐five families were generated via ‘natural’ spawning of multiple sets of five breeders (three dams × two sires) in individual brood tanks. Offspring from the 35 families were transferred abruptly from an acclimation temperature of ~24 °C to 5.7 °C and maintained subsequently at an average temperature of 6.5 °C. Offspring were assigned a posteriori to individual broodfish (dam and sire) based on genotypes at nuclear‐encoded microsatellites. Heritability of the survival–time probability function was estimated using a proportional hazard approach and an animal‐additive model. The estimated heritability was 0.20 (95% CI: 0.07–0.40), indicating a significant genetic component to acute cold‐stress tolerance in red drum.  相似文献   

16.
Red drum (Sciaenops ocellatus) is a euryhaline fish commonly found in the Gulf of Mexico and along the Atlantic coast of North America. Because of high commercial demand and its euryhaline characteristics, aquaculture of this species has diversified from marine to low-salinity aquaculture systems. In recent years, interest in the feasibility of producing red drum in inland freshwater systems has grown and this prompted us to investigate its osmoregulatory capacity after rearing for 8 months in a freshwater aquaculture system. We compared the activities of several genes and enzymes involved in the osmoregulatory process in freshwater-acclimatized (FW) and seawater (SW) red drum. The gene expression profiles were variable: the expression of genes encoding Na+/K+-ATPase (NKA) and the cystic fibrosis transmembrane regulator (CFTR) was slightly higher in SW than FW fish, while phosphoenolpyruvate carboxykinase (PEPCK) and the glucocorticoid receptor messenger RNA (mRNA) levels were higher in FW red drum. The total plasma K concentration was 60.3% lower, and gill NKA activity was 63.5% lower in FW than in SW fish. PEPCK activity was twofold higher in FW than in SW red drum. Similarly, liver glycogen was 60% higher in FW fish. In summary, both gene expression and the enzyme activity data support the phenotypic plasticity of red drum and suggest that the limited capacity for ion homeostasis observed, in particular the low plasma K concentration, was due to the composition of freshwater and does not necessarily reflect a physiological inability to osmoregulate.  相似文献   

17.
Heritability of juvenile growth rate was estimated for red drum (Sciaenops ocellatus), an economically important sciaenid fish in the southern USA. Thirty‐eight families were generated via ‘natural’ spawning of multiple sets of five breeders (three dams × two sires) in individual brood tanks. Offspring were individually tagged with Passive Integrated Transponder (PIT) tags and mixed for grow‐out in replicate ‘common‐garden’ tanks. Juvenile growth was followed from 166.4±18.6 to 254.0±27.0 mm (total length). Offspring were assigned a posteriori to individual brood fish (dam and sire) based on genotypes at nuclear‐encoded microsatellites. Heritability (h2) of a thermal growth coefficient was estimated using an animal‐additive model and a restricted maximum‐likelihood algorithm. Estimates of h2 were 0.33±0.08 and 0.31±0.08 for thermal growth coefficient based on length and weight respectively. These results indicate a significant genetic component in juvenile growth rate in red drum. Estimates of h2 for condition coefficient (K) at various measurement dates averaged 0.38, suggesting a genetic component to shape in juvenile red drum.  相似文献   

18.
Preliminary technical baseline information for the inland culture of juvenile red drum, Sciaenops ocellatus, in a freshwater fish hatchery is presented. Three initial stocking densities (d1 = 83, d2 = 167, and d3 = 250 fish/m3) were tested in a semirecirculation system for 575 days using a commercially available feed (48.1% protein, 25% lipids, and 0.13% fiber). Initial and final mean fish weight were 7.11 ± 0.02 g and 287.6 ± 27 g. As carrying capacity appeared to have been reached, only data from Days 1–333 were analyzed. One‐way ANOVA analyses indicated that the survival rate of the smaller density (d1 =40 ± 3.7%) was significantly different from the other two densities (d3 = 21 ± 1.1% and d2 = 23 ± 1.0%), which did not differ between them. Absolute growth rate (0.87 ± 0.02 g/day) was not significantly different between densities (F = 0.23. p = .801). Neither was weight significantly different between treatments. There were significant differences in the feed conversion rate (FCR) between densities (F = 8.54; p = .02). FCR for d1 was significantly lower than for the two other densities, which did not differ from each other. A von Bertalanffy growth model was adjusted (R2 = 0.95), and weight–length relationship presented negative allometric values (b = 2.85, R2 = 0.98).  相似文献   

19.
This study investigated variability in the growth, length, and age compositions and the rates of mortality of Flinders’ sillago Sillago flindersi exploited in a demersal trawl fishery in eastern Australia. Sampling was done over 2 years across three depth strata at two locations approximately 400 km apart. Ageing of sectioned sagittal otoliths indicated that the observed maximum age of females was 6 years and that of males 5 years, that growth was variable and that the von Bertalanffy growth parameters significantly differed according to gender and location. Females attained a greater L than males, but males displayed greater k values. The L values of both sexes and the mean length-at-age for fish aged 3–5 years were greater at the location of highest latitude. Length and age compositions differed according to depth, with smaller (<15 cm FL) and younger (<2 years) fish generally more predominant in the shallow (<30 m) strata than in the deeper (>31 m) strata. S. flindersi appear to use the shallow strata as a juvenile habitat, moving to deeper waters as they grow. This depth stratification between cohorts may reduce intraspecific competition and could potentially be used as a spatial management tool to reduce any fishing-associated impacts on juveniles. Fish between 1 and 3 years old dominated the age compositions of populations combined across all depths, with estimated total mortality ranging between 2.24 and 2.40. Fishing mortality ranged between 1.54 and 1.70 and was more than twice the derived natural mortality. Exploitation rates were approximately 0.70, indicating that the species was heavily fished.  相似文献   

20.
Two experiments were conducted to determine the nutritional value of various dietary proteins for juvenile red drum. In the first 8-week feeding trial, diets containing similar quantities of lipid, carbohydrate, available energy and ash with 35% crude protein from either lyophilized whole-body croaker (Micropogon undulatus), striated beef muscle, red drum processing waste or commercially processed menhaden (Brevoortia tyrannus) fish meal were fed to juvenile red drum in brackish (6 ppt) water along with a control diet containing lyophilized muscle of red drum. The control diet produced significantly (P<0.05) greater weight gain (WG), feed efficiency (FE), and protein efficiency ratio (PER) values than all other diets; intermediate responses were observed for fish fed diets containing protein from red drum waste and whole-body croaker, while diets containing striated beef muscle and menhaden fish meal yielded the lowest values. Some differences in tissue indices and body composition of red drum including hepatosomatic index, whole-body ash and lipid, as well as liver lipid and glycogen were induced by the various diets. In the second 8-week feeding trial, the control diet containing red drum muscle was compared with similar diets containing protein from whole-body croaker and menhaden fish meal. Again the control diet produced the greatest WG, FE, and PER values followed by whole-body croaker and then menhaden fish meal. Effects of the dietary proteins on tissue indices and body composition were limited. The excellent protein quality and low-temperature processing of lyophilized red drum muscle resulted in superior performance of red drum relative to the other evaluated protein products, and lyophilized whole-body croaker provided better performance than commercially processed menhaden fish meal.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号