Improving Weight-Length Relationships in Fish to Provide More Accurate Bioindicators of Ecosystem Condition

Courtney, Ya'el; Courtney, Joshua; Courtney, Michael

doi:10.5296/ast.v2i2.5666

Cited by 13 publications

(17 citation statements)

References 11 publications

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“…As seen in Figure 3, the set of conditions with positive exponents, relative errors of 0.05, and the scaling parameter value L = 5 converged well for the proposed model, demonstrating that a more conclusive result may be found for certain sets of conditions. In agreement with the previous study [4], the relative uncertainties and errors of the exponent parameter b were comparable for the traditional and proposed models, with each law producing very close mean and RMS values for b, as seen in Figure 4. Due to this, it can be seen that the difference in accuracy and precision between models is confined to the coefficient or scaling parameter.…”

Section: Resultssupporting

confidence: 90%

“…The scaling power law model from the previous study [4] has been applied to data gathered from two species of trout in a Colorado reservoir [5], where it assisted in demonstrating that the trout were in poor health. Other potential applications of the proposed scaling version of the power law model include further ecological applications, but also have consequences in a wider array of fields, such as physics and chemistry.…”

Section: Applicationsmentioning

confidence: 99%

“…Previous studies regarding weight-length relationships in fish ( [4], and references therein) demonstrated that a power law of the form f (x) = ( x L ) b reduced uncertainties in parameter values, which were determined with NLLS fitting using the Levenberg-Marquardt algorithm, by replacing the coefficient a of the traditional model with the scaling parameter L. The previous studies were limited to exponents with values close to 3, and therefore more research is needed to test the idea in a wider range of data sets.…”

Section: Introductionmentioning

confidence: 99%

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An Improved Power Law for Nonlinear Least-Squares Fitting?

Helyer¹,

Courtney²

2017

Data

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Models based on a power law are prevalent in many areas of study. When regression analysis is performed on data sets modeled by a power law, the traditional model uses a lead coefficient. However, the proposed model replaces the lead coefficient with a scaling parameter and reduces uncertainties in best-fit parameters for data sets with exponents close to 3. This study extends previous work by testing each model for a range of parameters. Data sets with known values of scaling parameter and exponent were generated by adding normally distributed random errors with controlled mean and standard deviations to underlying power laws. These data sets were then analyzed for both forms of the power law. For the scaling parameter, the proposed model provided smaller errors in 96/180 cases and smaller uncertainties in 88/180 cases. In most remaining cases, the traditional model provided smaller errors or uncertainties. Examination of conditions indicates that the proposed law has potential in select cases, but due to ambiguity in the conditions which favor one model over the other, an approach similar to the one in this study is encouraged for determining which model will offer reduced errors and uncertainties in data sets where additional accuracy is desired.

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Section: Resultssupporting

confidence: 90%

Section: Applicationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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An Improved Power Law for Nonlinear Least-Squares Fitting?

Helyer¹,

Courtney²

2017

Data

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“…This model has been shown to yield smaller uncertainties in the parameters L 1 , which is the typical length of the fish weighing 1 kg, and the exponent b. (Courtney et al, 2014;Dexter et al, 2011;Keenan et al, 2011;Cole-Fletcher et al, 2011).…”

Section: Methodsmentioning

confidence: 99%

“…This is much longer than the 450 mm which is ISSN 2168-9148 2015 the more common length of a fish weighing 1 kg (Carlander 1969). As a bioindicator, such a large value of L 1 suggests poor fish condition (Courtney et al, 2014). Figure 2 shows relative weight vs. length for 100 brown trout.…”

Section: Methodsmentioning

confidence: 99%

Relative Weight of Brown Trout and Lake Trout in Blue Mesa Reservoir, Colorado

Abbott

Schmidt²,

Courtney

2014

AST

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Published data concerning the standard weight in lake trout (Salvelinus namaycush) and brown trout (Salmo trutta) have been established. The standard weights were used to compute relative weights for data collected in the spring and summer of 2011 for brown trout and lake trout in the Blue Mesa Reservoir, Colorado. The mean relative weight of a sample of 100 brown trout ranging in length from 260 to 432 mm was 71.72 +/-0.90, showing that the brown trout were in poor condition. The mean relative weight of a sample of 17 lake trout ranging in length from 387 to 689 mm was 86.57 +/-2.40, showing that the lake trout were also in poor condition. Using least squares regression, a best fit curve was determined for weight (W) vs. total length (L) in the brown trout, W(L)=1000(L/517.49) 2.5746 , where W is in grams, and L is in millimeters.

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Lipophrys pholis is larger, grows faster and is in better condition in protected than in unprotected rocky shores

Compaire,

Visintini,

Soriguer

et al. 2024

Aquatic Conservation

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Intertidal fish are a key component of littoral food webs, contributing to the diets of birds and commercial fish species. Ascertaining their growth and condition can therefore help understand the health status of local communities. Lipophrys pholis is a fish of the rocky intertidal with a wide distribution throughout the North‐eastern Atlantic (NE Atlantic) that has been recommended for use as an indicator in the environmental biomonitoring of marine ecosystems. However, it is unclear yet if this species is sensitive to the reserve effect. In this study, the size, growth and body condition of specimens caught at protected and unprotected rocky shores of two contrasting marine provinces of the NE Atlantic were analysed to address whether L. pholis is sensitive to the reserve effect. L. pholis were larger, grew faster in weight and were in better condition in the protected shores of both provinces. A faster growth rate was observed in the populations of the warmer province. Inshore waters of unprotected sites in the Northern European Seas sampled in this study have recently been incorporated into a protected area. Thus, these results can help assess the success of the marine conservation programme and the time L. pholis needs to improve its population's health at these shores. Regulating access to shores to avoid trampling and harvesting is a protection measure that can help enhance the health and conservation of L. pholis populations.

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Improving Weight-Length Relationships in Fish to Provide More Accurate Bioindicators of Ecosystem Condition

Cited by 13 publications

References 11 publications

An Improved Power Law for Nonlinear Least-Squares Fitting?

An Improved Power Law for Nonlinear Least-Squares Fitting?

Relative Weight of Brown Trout and Lake Trout in Blue Mesa Reservoir, Colorado

Lipophrys pholis is larger, grows faster and is in better condition in protected than in unprotected rocky shores

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