Mathematical Description of Trout‐Stream Fisheries
01 Nov 1980-Transactions of The American Fisheries Society (Taylor & Francis Group)-Vol. 109, Iss: 6, pp 587-602
TL;DR: A mathematical model of trout-stream fisheries was developed that can be used to evaluate a variety of fishing regulations and found density-dependent mortality was found in the first 2 years of life for each of the two brook trout and three brown trout populations studied in Michigan.
Abstract: A mathematical model of trout-stream fisheries was developed that can be used to evaluate a variety of fishing regulations. Density-dependent mortality was found in the first 2 years of life for each of the two brook trout (Salvelinus fontinalis) and three brown trout (Salmo trutta) populations studied in Michigan. Regression equations were used to describe the density-dependent relationships for modeling purposes. Equations were developed that used mortality, growth, and length-frequency information to calculate the number of fish in a population, number caught and harvested, number caught and released, number of deaths due to hooking mortality, number of natural deaths, and number recruited for any time period and age-group. Also, addition of a length-weight regression allowed equations to be developed for calculating yield in weight harvested, yield in weight caught and released, and gross biomass production for any time period and age-group. Effects of imposing different types of length limit...
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TL;DR: A general age- and size-structured population model calibrated to several recreationally important fish species found harvest slots to represent a valuable option to meet both conservation and recreational fisheries objectives.
Abstract: Managing fisheries using length-based harvest regulations is common, but such policies often create trade-offs among conservation (e.g. maintaining natural agestructure or spawning stock biomass) and fishery objectives (e.g. maximizing yield or harvest numbers). By focusing harvest on the larger (older) fish, minimumlength limits are thought to maximize biomass yield, but at the potential cost of severe age and size truncation at high fishing mortality. Harvest-slot-length limits (harvest slots) restrict harvest to intermediate lengths (ages), which may contribute to maintaining high harvest numbers and a more natural age-structure. However, an evaluation of minimum-length limits vs. harvest slots for jointly meeting fisheries and conservation objectives across a range of fish life-history strategies is currently lacking. We present a general age- and size-structured population model calibrated to several recreationally important fish species. Harvest slots and minimum-length limits were both effective at compromising between yield, numbers harvested and catch of trophy fish while conserving reproductive biomass. However, harvest slots consistently produced greater numbers of fish harvested and greater catches of trophy fish while conserving reproductive biomass and a more natural population age-structure. Additionally, harvest slots resulted in less waste in the presence of hooking mortality. Our results held across a range of exploitation rates, life-history strategies and fisheries objectives. Overall, we found harvest slots to represent a valuable option to meet both conservation and recreational fisheries objectives. Given the ubiquitous benefits of harvest slots across all life histories modelled, rethinking the widespread use of minimum-length limits is warranted.
147 citations
Cites background from "Mathematical Description of Trout‐S..."
...Some theoretical studies on the effectiveness of HSs have been conducted, but they were focused on a species-specific level (Arlinghaus et al. 2010 for northern pike Esox lucius, Esocidae, Clark et al. 1980; Jensen 1981; Garc ıa-Asorey et al. 2011 for various freshwater salmonids including the anadromous steelhead Oncorhynchus mykiss, Salmonidae, and Koehn and Todd 2012 for Murray cod, Maccullochella peelii, Percichthyidae)....
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...Second, length-based harvest limits are intended to manage the size-structure of fish stocks to meet expectations of anglers (Clark et al. 1980; Jensen 1981; Noble and Jones 1999)....
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...…of HSs have been conducted, but they were focused on a species-specific level (Arlinghaus et al. 2010 for northern pike Esox lucius, Esocidae, Clark et al. 1980; Jensen 1981; Garc ıa-Asorey et al. 2011 for various freshwater salmonids including the anadromous steelhead Oncorhynchus mykiss,…...
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...Second, length-based harvest limits are intended to manage the size-structure of fish stocks to meet expectations of anglers (Clark et al. 1980; Jensen 1981; Noble and Jones 1999)....
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TL;DR: It is found that, compared to the traditional regulatory approach of management by small minimum-length limits, preservation of large and old individuals through harvestable-slot length limits promises considerable benefits for fisheries quality, without compromising the long-term conservation of the population.
104 citations
Cites result from "Mathematical Description of Trout‐S..."
...This conclusion is in line with earlier research in freshwater salmonids (Clark et al., 1980; Jensen, 1981), but shall not be uncritically transferred to other life-histories that differ strongly from pike biology....
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TL;DR: A yield-per-recruit simulation model is used to evaluate the effect of poaching on legal harvest in sport fisheries and results depict the degree of reduction in legal harvesting in minimum-size fisheries with 0-100% (in 10% increments) illegal harvest.
Abstract: The degree of compliance with a fishing regulation can have a significant impact on the regulation's effectiveness. In this paper, we use a yield-per-recruit simulation model to evaluate the effect of poaching on legal harvest in sport fisheries. Two types of illegal harvest were considered: harvest of fish below the legal size limit and harvest of fish from catch-and-release fisheries. The results depict the degree of reduction in legal harvest in minimum-size fisheries with 0-100% (in 10% increments) illegal harvest. For brook trout Salvelinus fontinalis, the reduction in legal harvest ranged from 11% at 10% illegal harvest to 72% at 100% illegal harvest; these reductions ranged from 10 to 66% for northern pike Esox lucius, 8 to 57% for brown trout Salmo trutta, and 2 to 22% for largemouth bass Micropterus salmoides. In catch-and-release fisheries, illegal harvest reduces the number offish caught and released. Most ofthe benefits ofcatch-and-release regulations, in terms of increased numbers an...
80 citations
Cites background from "Mathematical Description of Trout‐S..."
...1967); (2) largemouth bass Micropterus salmoides in Kent Lake, a 400-hectare reservoir (Goudy 1981); (3) brown trout Salmo trutta in the Au Sable River, a 30-m-wide river (Clark et al. 1980); and (4) northern pike Esox Indus in a lake (Latta 1972)....
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TL;DR: The current declining trend of brown trout could be reduced by river-specific management and alternative fishing regulations, and seem to depend on the environmental and biological characteristics of the populations.
Abstract: Spanish brown trout, Salmo trutta L., populations are currently overexploited as a result of unsuitable management activities, and their genetic uniqueness is threatened by introgression of foreign genes because of stocking. In this study, the status and management of trout fisheries were reviewed and the effects of fishery management on abundance, production and life history of trout in Spain assessed. Angling exploitation has reduced the mean age, the age diversity and number of trout exceeding the minimum size in exploited sections. Likewise, exploited areas show a general decrease in overall abundance parameters and production, as well as a depletion of the breeding stock and population fecundity. Current minimum size limit control reduces the spawning chances in fast-growing populations because of higher susceptibility to angling harvest. The effects of fishery management on population dynamics, production and life-history characteristics exhibit different patterns among Spanish rivers, and seem to depend on the environmental and biological characteristics of the populations. The current declining trend of brown trout could be reduced by river-specific management and alternative fishing regulations.
77 citations
TL;DR: In this paper, neural networks and multiple linear regression models were developed from combinations of physical habitat variables in 220 channel morphodynamic units (pools, riffles, runs, etc.) of 11 different streams in the central Pyrenean mountains.
Abstract: Neural networks and multiple linear regression models of the abundance of brown trout (Salmo trutta L.) on the mesohabitat scale were developed from combinations of physical habitat variables in 220 channel morphodynamic units (pools, riffles, runs, etc.) of 11 different streams in the central Pyrenean mountains. For all the 220 morphodynamic units, the determination coefficients obtained between the estimated and observed values of density or biomass were significantly higher for the neural network (r2 adjusted= 0.93 and r2 adjusted=0.92 (p<0.01) for biomass and density respectively with the neural network, against r2 adjusted=0.69 (p<0.01) and r2 adjusted = 0.54 (p<0.01) with multiple linear regression). Validation of the multivariate models and learning of the neural network developed from 165 randomly chosen channel morphodynamic units, was tested on the 55 other channel morphodynamic units. This showed that the biomass and density estimated by both methods were significantly related to the observed biomass and density. Determination coefficients were significantly higher for the neural network (r2 adjusted =0.72 (p<0.01) and 0.81 (p<0.01) for biomass and density respectively) than for the multiple regression model (r2 adjusted=0.59 and r2 adjusted=0.37 for biomass and density respectively). The present study shows the advantages of the backpropagation procedure with neural networks over multiple linear regression analysis, at least in the field of stochastic salmonid ecology.
72 citations
References
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01 Jan 1975
5,417 citations
5,058 citations
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30 Jun 1993
TL;DR: Pitcher and Pauly as mentioned in this paper used a simple theory of fishing, illustrated by analysis of a trawl factoy, to give the annual yield in weight from a fishery in a steady state.
Abstract: Series foreword AJ Pitcher Foreword D Pauly Part One: Fundamentals of the theory of fishing, illustrated by analysis of a trawl factoy Introduction:- theoretical methods in the study of fishery dynamics The basis of a theoretical model of an exploited fish population and definition of the primary factors Mathematical representation of the four primary factors Recruitment Natural mortality Fishing mortality Growth A simple model giving the annual yield in weight from a fishery in a steady state Adaptation of the simple model to give other characteristics of the catch and population Part Two: Some extensions of the simple theory of fishing Recruitment and egg-production Natural mortality Fishing mortality and effort Growth and feeding Spatial variation in the values of parameters movement of fish within the exploited area Mixed populations:- the analysis of community dynamics Part Three: Estimation of parameters Relative fishing power of vessels and standardisation of commercial statistics of fishing effort Estimation of the total mortality coefficient (F + M), and the maximum age, t* Seperate estimation of fishing and natural mortality coefficients Recruitment and egg-production Growth and feeding Part Four: The use of theoretical models in a study of the dynamics and reaction to exploitation of fish populations Application of population models of part one Application of population models of part two Principles and methods of fishery regulation Requirements for the regulation of the North Sea Demersal fisheries Appendices Bibliography and author index Subject index List of amendments compiled by the American Fisheries Society
4,489 citations
TL;DR: In an attempt o synthesize a useful general hypothesis for natural regulation of populations, Hairston, Smith, and Slobodkin (1960) concluded that plants are limited or controlled by a shortage of nutrients, light, or water, or are resource-limited.
Abstract: In an attempt o synthesize a useful general hypothesis for natural regulation of populations, Hairston, Smith, and Slobodkin (1960) concluded that plants are limited or controlled by a shortage of nutrients, light, or water, or are resource-limited. Herbivorous trophic groups, they suggested, are largely controlled by predation, while predator and decomposer groups are food-limited. In other words, all trophic groups but the herbivores are resource limited. Of course this hypothesis is a general and broad one. Looking at specific animals of a given trophic group it is difficult o find a common mechanism of population regulation. In some cases man's influence has changed the mode of control from predator to food, as has occurred in many big-game populations. For some freshwater fish populations, Larkin (1956) indicates that climatic controls seem to outweigh biological factors in controlling numbers. Possibly this could be explained by environmental stability. In unstable situations climate may prevail as more than a \"density legislative\" (Nicholson, 1954) factor. In more benign environments, intraand inter-specific competition and predation become more important as \"density governors\" in the stable framework legislated by the physical environment. Larkin suggests that in such situations inter-specific competition predisposes fish to loss from other causes, notably predation. Larkin states that freshwater environments offer comparatively little opportunity for specialization in fish (when compared with terrestrial environments). Therefore, many species have wide tolerance of habitat type and flexible feeding habits, leading to breadth at each level of the food chain rather than height of a pyramid of numbers.
464 citations
TL;DR: Size-selective mortality decreases or increases the actual and back-calculated lengths of an age-group, while at the same time altering the shape and variance of its length frequency distribution only slightly or not at all.
Abstract: Size-selective mortality decreases or increases the actual and back-calculated lengths of an age-group, while at the same time altering the shape and variance of its length frequency distribution o...
278 citations