Length-weight Data Research Articles

Ruffe Length–Weight Relationships with a Proposed Standard Weight Equation

AbstractRuffe Gymnocephalus cernuus length–weight data from 141 data sets were obtained from a variety of waters across Europe and the Laurentian Great Lakes for summarization and development of standard weight (Ws) equations. The mean slopes of the length–weight relationships from all populations and for all percentiles except the 95th percentile were not different from 3.0, suggesting that ruffe growth is generally isometric. The Ws equations developed using the regression line percentile, linear empirical percentile (EmP), and Froese's methods exhibited length‐related biases. The quadratic EmP Ws equations for the 75th and 50th percentiles did not exhibit length‐related biases and thus can be used to compute the relative weight of ruffe. The EmP 75th percentile Ws equation was log10(Ws75) = −2.5800 + 0.6210·log10(total length, TL) + 0.6073·[log10(TL)]2, and the 50th percentile Ws equation was log10(Ws50) = −3.3524 + 1.3969·log10(TL) + 0.4054·[log10(TL)]2 when constrained to ruffe between 55 and 205 mm TL. We propose that the minimum TL for a five‐cell length categorization system used to compute stock indices for ruffe be 55, 90, 120, 140, and 175 mm TL. These results provide a method for computing relative weight indices for typical (50th percentile) and above‐average (75th percentile) ruffe; this method will allow comparisons of body condition across time, among habitats, among bodies of water, and among length categories.

Length-Weight Relationships of Select Common Nearshore Southern California Marine Fishes

Growth dynamics of marine fish is often critical for fisheries analysis. Frequently only lengths are measured during ecological surveys, occasionally with aggregate weights by species (Allen and Herbinson 1990; Pondella and Allen 2000; Allen et al. 2002). This information often allows for estimation of age-class composition through length frequency analysis, but can mask the importance of individual fish weights to the overall community structure, such as the inclusion of one, or a few, large individuals among a predominantly small catch. Over time, authors have reported length-to-weight relationships for specific species in the course of specific life history investigations, but these studies are rarely conducted on forage species. Cailliet et al. (2000) compiled many of the relationships that were available at the time, but numerous species still lack such basal information. Their database, however, contained 124 species, many of which did not have length-weight relationships available. Love et al. (2002) also compiled additional information on several rockfish species (Sebastes spp) and Sebastolobus alascanus. Since 1979, impingement surveys at coastal generating stations routinely recorded the length of nearly all impinged fish during a given survey. Most of these surveys, however, recorded the aggregate weight by species, a protocol consistent with most ecological studies in southern California. Specific, focused studies were occasionally undertaken during which the individual length and weight of a subset of individuals were recorded. Moreover, instances when only a single individual of a specific species was impinged, a defacto length-weight relationship data point was recorded. During these studies the appropriate length; standard (SL), total (TL), or disc width (DW) was measured to the nearest millimeter (mm) and weight recorded to the nearest gram (g). Data from impingement records 2001–2006, recorded at generating stations from San Diego County to Los Angeles County, California were reviewed to generate speciesspecific length-weight relationships (Tables 1 and 2). A total of 59 species were identified with length and weight recorded for greater than 10 individuals. These included both 54 ray-finned fishes (Class Actinopterygii) and 5 elasmobranch species (Subclass Elasmobranchii). All were common to the Southern California Bight (Miller and Lea 1972; Love et al. 2005). Forty-two of these species were included in the Cailliet et al. (2000) species list, but only 27 had a length-weight relationship listed. The length-weight relationships of fishes typically fit the non-linear equation W 5 aL, where W 5 weight (g), L 5 length (mm), and a and b are derived constants. A best fit line was plotted for each distribution using MS Excel. The determination of the best fit was based on the R-value. Fifty-six species were best described by the traditional non-linear equation W 5 aL. Two species, Anchoa compressa and A. delicatissima were best described by a linear relationship and one species, Seriphus politus, was best described by an exponential function. The minimum and maximum length (mm) recorded for each

Relationships between Relative Weight, Prey Availability, and Growth of Walleyes in Oneida Lake, New York

AbstractAssessment of predator–prey dynamics is a central feature of community‐based fisheries management, and a variety of fish condition indices have been developed from length–weight data to make inferences about feeding conditions. Relative weight (Wr) is useful for measuring fish condition, is easily calculated, and has simple data requirements; however, few studies have empirically validated Wr indices. We compared the Wr of walleyes Sander vitreus in Oneida Lake, New York, with prey fish availability and walleye growth observed over 23 years (1961–1983). For each year, we calculated the Wr for three length‐classes (350, 400, and 450 mm total length) of walleyes caught in October. Prey fish availability was calculated from annual estimates of (1) prey biomass in bottom trawl catch and (2) biomass of age‐3 and older walleyes estimated from mark–recapture studies. Growth of walleyes (ages 4–6) was determined using lengths at age that were back‐calculated from scale annuli. The Wr declined as walleye length‐class increased, and Wr was positively related to both prey fish availability and walleye growth. Our study suggests that Wr can be a useful tool for describing feeding conditions and assessing predator–prey relations.

Estimating Fish Body Condition with Quantile Regression

AbstractWe used quantile regression to compare the body condition of walleye Sander vitreus and white bass Morone chrysops before (1980–1988) and after (1989–2004) the establishment of alewives Alosa pseudoharengus in Lake McConaughy, Nebraska. Higher quantiles (percentiles = 100% × quantiles (0, 1)) of weight (W) at the same total length (TL) were indicative of better body condition in an allometric growth model that included separate slopes and intercepts for the before and after groups. All quantiles of walleye weights by TL increased in the years after alewife introduction, ranging from 1.01 to 1.12 times weights in the years before alewife introduction, with greatest increases for the lower (<0.50) quantiles and greater TLs. Quantiles up to 0.25 (the lowest 25th percentiles) of white bass weights were reduced in years after alewife introduction for TLs less than 300 mm, ranging from 0.78 to 0.98 times weights in the years before alewife introduction. However, quantiles greater than or equal to 0.50 (the upper 50th percentiles) of white bass weights increased for all TLs, ranging from 1.01 to 1.06 times the pre‐1988 weights. A three‐group analysis, which improved the model fit for longer white bass, indicated a reduction (0.80–1.0) in white bass body condition across all TLs in the first 2 years (1989–1990) after alewife introduction, whereas body condition actually improved (1.02–1.12) across all TLs in later years (1991–2004). Thus, after the establishment of alewives in 1988, walleye body condition improved for all fish at all lengths (the greatest improvement occurring among fish in poorer condition), whereas white bass body condition was initially reduced for all fish at all lengths for 2 years and improved in subsequent years. The approach that we developed for comparing fish body condition before and after a management action in Lake McConaughy could be applied to other weight–length data sets typically evaluated with relative weight indices.

Monte Carlo evaluation of a nonlinear regression estimator for aggregated length–weight data

Parameters of fish length–weight relationships (W = aLb) are usually estimated by applying linear regression to log-transformed length and weight values, but measuring individual weights is time-consuming and expensive. Often, length and weight data are available as sets of length measurements and aggregated sample weights, and the aggregate average weight of a sample can be expressed as the average of the weights predicted for the individual fish lengths. This study evaluated the feasibility of applying nonlinear regression to aggregated length–weight data. Experiments with simulated random length–weight data demonstrated that the estimates of parameter b appear to be unbiased and the estimates of a are right-skewed and biased. Further, the estimates of ln(a) and b are almost perfectly correlated. The precision and accuracy of the estimates were greatly influenced by the number of aggregate samples but were relatively unaffected by the number of fish in each sample. An additional experiment showed that the residuals from the regression can be used to detect small changes in the length–weight parameters.

150PREGNANCY AND PARTURITION FOLLOWING TRANSFER OF BOVINE EMBRYOS CULTURED IN TWO MEDIA UNDER TWO OXYGEN CONCENTRATIONS

Developmental aberrations following transfer of in vitro-produced bovine embryos can result in early gestational losses and offspring abnormalities. An ongoing study tests the hypothesis that such aberrations occur with equal frequency among commonly employed culture systems. In year 1, embryos were produced using oocytes from abattoir-derived ovaries (breed unspecified) and a proven Angus bull selected for low birth weight. IVC treatments were 2×2 factorial for medium (KSOMaa or SOFaa) and oxygen concentration (5% or 20%). Angus recipients (n=61; 32 cows, 29 heifers) were randomly allotted to treatments for Day 7 transfers. Pregnancy was diagnosed with ultrasound several times during gestation (Table 1). At parturition calf weight, shoulder height, chest circumference, crown-rump length, and humeral and femoral length data were collected. Statistical analyses (Statistical Analysis System, Cary, NC) were logistic regression with a binomial distribution for pregnancy rate, and the general linear models procedure for calf measurements; included were fixed effects of medium, oxygen, and their interaction, with additional fixed effects of dam parity and calf sex where appropriate. No significant effects of medium or oxygen were found for pregnancy rate or calf measurements other than birth weight. Mean birth weight was higher in the KSOM, 20% oxygen treatment (Table 1), and medium-oxygen interaction for calf weight was also significant (P<0.01). In year 2 embryos were produced using the same Angus bull and Angus oocytes. Angus recipients (n=38; 32 cows, 6 heifers) were randomly allotted to treatments. Fetal crown-rump lengths were measured by ultrasound weekly from Days 33 to 54 and were analyzed as repeated measures using the mixed procedure. Pregnancy outcome and LS means for crown-rump lengths are included in Table 1. Though insufficient recipient numbers preclude determination of statistical significance, of interest is the relatively small fetal size in early gestation and large birth weights in the KSOM, 20% oxygen treatment. This treatment also contained a Day 33 pregnancy, subsequently lost by Day 40, in which the fetus was too small to obtain an accurate measurement. Fetal growth will continue to be monitored throughout gestation. Data will be collected at parturition as in year 1, and pooled analyses will be done. Table 1

The Effects of Food Type on Length-Weight Growth, Sexual Differentiation, and Survival in Chirocephalus Ruffoi (Anostraca) Cultured under Standard Conditions

Abstract Nauplii of the anostracan Chirocephalus ruffoi were grown until sexual differentiation under standard laboratory conditions (18 ± 1°C temperature; 12L/12D photoperiod; 1600 lux intensity; 200 individuals L−1 density) and fed algae (Selenastrum capricornutum), baker's yeast (Saccharomyces cerevisiae), or a lipid-enriched yeast (Lansy PZ). In parallel experiments, we evaluated survival, development, and increase in body length and weight (wet and dry). Differences among the treatments were analyzed by ANCOVA and Newman-Keuls multiple range tests. The length-weight growth data, log-transformed, were fitted using an orthogonal least squares method. The results show that food type has marked effects on the growth rate and survival of the animals. As previously shown in terms of nutritional effectiveness, enriched yeast produces the best culture results.

Short communication: Virulence of different isolates causing verticillium wilt of pepper in the Padrón region

A survey of verticillium wilt of pepper was carried out in farms of the Padrón region, including both greenhouses andfields. Pepper plants cv. Padrón showing wilt symptoms were collected in three successive sampling sessions performedfrom May to October 1997. A total number of 79 isolates of Verticillium dahliae Kleb were obtained. The high frequencyof farms with plants infected with V. dahliae, especially at the end of the crop season, was related to a high persistenceof the fungus during the whole of the 1990s. Twenty-two isolates were tested for pathogenicity, and all of them were ableto induce wilting in cv. Padrón pepper plants. Dry weight and stem length data of inoculated plants showed that there wasa high variability in the virulence of the isolates tested, and significant differences were observed among them.

Considerations on the diet composition and feeding rate of dermersal sharks in 15 European public aquaria

AbstractTo get an overview of the feeding practices applied to dermersal sharks in captivity, a questionnaire was sent to 15 European public aquaria. The most common dermersal shark species kept in the participating aquaria are Carcharhinus plumbeus (n=9), Carcharias taurus (n=7), and C. melanopterus (n=6). Body weight (BW) was calculated using captive estimated body length (BL) and actual weight data obtained from commercial fisheries. The estimated BW for C. plumbeus in all participating aquaria is higher than the calculated BW. The feeding rate (FR) for adult C. plumbeus varied widely within participating aquaria (2.3–11.5% BWcal/week or 32–112 kcal/kg BWcal/week). The FR for adult C. plumbeus was lower (1.2–7.9% BWest/week or 17–99 kcal/kg BWest/week) using the estimated BW. Adult Carcharias taurus were fed at 1.3–5.0% BWcal/week or 70–170 kcal/kg BWcal/week. Negaprion brevirostris was fed at 5.0% BWest/week or 57 kcal/BWest/week. The relationship between FR and estimated BW is expressed as FR=54.5 e−0.033BW. In this study, the feeding frequency for C. plumbeus varied between 1–7 times a week, with an average of 3.3 times a week. Diet in all aquaria consisted of both lean and fatty fish, and sometimes squid or crustaceans. Supplementation of vitamins is common practice in 80% of the surveyed aquaria, although a wide variety of quantity and quality was observed. Ten aquaria (66%) add iodine, as potassium iodide (0.4–12.5 mg KI/kg BW/week) or calcium‐iodate (322–1,500 mg/kg food/week), to their food. Zoo Biol 22:203–226, 2003. © 2003 Wiley‐Liss, Inc.

Root proliferation in perennial grasses of low and high palatability

Root proliferation of desirable (Stipa clarazii andS. tenuis) and undesirable (S.ambigua)perennial grasses was studied in semiarid rangelands of Central Argentina(40°39′S, 62°54′W) in 1998. On 17 September, soil coreswereremoved from the edge of the plant, metal structures lined with screen mesh(hereafter called bags) were buried in the holes, and root-free soil was placedinto these structures. Numbers of green tillers and circumference per plant hadpreviously been determined. Since plants were of unequal size among species,root length and root dry weight data are reported on a per green tiller basis.Half of the plants was defoliated to 5 cm stubble height on 17September and/or 12 October, while the other half remained undefoliated(controls). Bags were destructively harvested either 20 days after the firstdefoliation (first sampling) or 56 days after the second defoliation (secondsampling) by digging out soil very carefully around each bag. Roots were washedfrom soil, root length estimated by the line intercept method, root dry weightdetermined after oven-drying, and root length per unit root dry weightcalculated from the two measured variables. Root length and dry weight weremorethan 96% greater on defoliated and undefoliated plants ofS. clarazii than on those of S.tenuisor S. ambigua for both sampling dates. Root length perunitroot dry weight, however, was more than 43% greater (p < 0.05) inS. tenuis than in S. clarazii andS. ambigua during the second sampling. Defoliated plantshada similar root length and root dry weight than undefoliated plants in all threespecies, although plants of S. tenuis defoliated twiceshowed a greater (p < 0.05) root length than undefoliated controls. Rootlength and root dry weight were similar between sampling periods, except onundefoliated plants of S. tenuis which had a greater (p<0.05) root length and root dry weight at the first than at the second sampling.Although root length per unit root dry weight may be greater inS. tenuis than in S. clarazii andS. ambigua, greater root length and dry weight increasesinS. clarazii after defoliation appear determinant incontributing to explain its greater competitive ability and defoliationtolerance when compared with the other two species.Nomenclature of taxa followed.

Growth, Survival, and Feed Conversion Rates of Hatchery‐Reared Mutton Snapper Lutjanus analis Cultured in Floating Net Cages

Abstract.— The aquaculture performance of mutton snapper Lutjanus analis raised in floating net cages was assessed by measuring their growth, survival, and feed conversion rates during a growout trial conducted in a 3.2‐ha saltwater lake in the Florida Keys, Florida, USA. Approximately 10,500 hatchery‐reared finger‐lings were stocked in two circular, high‐density polyethylene (HDPE) net cages of 7‐m diameter × 7‐m deep (300 m2) and 10‐m diameter × 7‐m deep (600 m3) dimensions. Cages were stocked at 25 fish/m3 (3.2 kg/m3) and 5 fish/m3 (0.72 kg/m3), respectively. Fish grew from a mean of 16.5 g to 302.8 g (25.6 cm TL) in 246 days in the former cage and from a mean of 42.3 g to 245.6 g (23.8 cm TL) in 178 d in the latter cage. Growth rates in weight were best expressed by the following exponential equations: cage 1 (high stocking density): W = 20.716 e0.0112x (r2= 0.83); cage 2 (low stocking density): W = 38.848 e0.0118x (r2= 0.81). Length‐weight data indicate that hatcheryraised, cage‐cultured mutton snapper are heavier per unit length than their wild counterparts. There was no significant difference (P &lt; 0.05) between the slopes of the two lines, indicating that fish in the two cages grew at the same rate. The length‐weight relationships for mutton snapper stocked in cages 1 and 2 are expressed, respectively, by the equations W = 0.000009 L 3.11 (r2= 0.99) and W = 0.000005 L 3.22 (r2= 0.97). Overall feed conversion rate for both cages combined was 1.4. Approximately 10% of the fish sampled exhibited some degree of deformity, particularly scoliosis. Overall survival rate was 70%. Results suggest that L. analis has potential for aquaculture development in net cage systems.

Use of Regional Standard Weight (Ws) Equations to Assess Body Condition of Brown Trout (Salmo trutta) from Metal-Contaminated Streams

ABSTRACT Weight-length relationships provide a tool to assess the body condition of brown trout (Salmo trutta) populations inhabiting stream reaches where stressors, such as metals, have chronic, sub-lethal toxic impacts. A previously published brown trout standard-weight equation, Ws, overestimated Colorado brown trout weights. Weight-length data from 16 Colorado brown trout populations (n = 9, 8 16) were used to develop a regional standard weight (Wcl) equation based on fish from waters free of metal contamination. Relative-weights (Wr) were then compared between metal-contaminated and metal-free streams in Colorado using the Wcl equation. Brown trout Wr's were lower in metal contaminated streams than in stream reaches uncontaminated by metals. The development and use of regional standard weight equations is recommended to help assess the weight of brown trout inhabiting metal-contaminated stream reaches.

A Test of Factors Hypothesized to Influence Biomass of Salmonids in Rocky Mountain Streams

ABSTRACT Weight-length relationships provide a tool to assess the body condition of brown trout (Salmo trutta) populations inhabiting stream reaches where stressors, such as metals, have chronic, sub-lethal toxic impacts. A previously published brown trout standard-weight equation, Ws, overestimated Colorado brown trout weights. Weight-length data from 16 Colorado brown trout populations (n = 9, 8 16) were used to develop a regional standard weight (Wcl) equation based on fish from waters free of metal contamination. Relative-weights (Wr) were then compared between metal-contaminated and metal-free streams in Colorado using the Wcl equation. Brown trout Wr's were lower in metal contaminated streams than in stream reaches uncontaminated by metals. The development and use of regional standard weight equations is recommended to help assess the weight of brown trout inhabiting metal-contaminated stream reaches.

Application of the Relative Weight Index to Juvenile Walleyes

Weight-length data for juvenile walleyes Stizostedion vitreum from 39 populations (N = 2,006) in seven states were used to develop a standard weight (Ws) equation. We used the regression-line-percentile technique, which provides a 75th-percentile standard, to develop the equation. The proposed Ws equation is log10 Ws(g) = −4.804 + 2.869 log10total length (TL, mm). The equivalent in English units is log10 Ws(lb) = −3.431 + 2.869 log10TL(in). The walleye Ws equation is valid for juvenile fish between 30 and 149 mm. This proposed Ws equation should serve as a basis for further evaluation of Wr as an index and the continued development of Ws equations for juvenile fishes.

Hypertrophy of skeletal muscle in diabetic rats in response to chronic resistance exercise.

This study had the following objectives: 1) to determine whether diabetic rats could increase muscle mass due to a physiological manipulation (chronic resistance exercise), 2) to determine whether exercise training status modifies the effect of the last bout of exercise on elevations in rates of protein synthesis, and 3) to determine whether chronic resistance exercise alters basal glycemia. Groups consisted of diabetic or nondiabetic rats that performed progressive resistance exercise for 8 wk, performed acute resistance exercise, or remained sedentary. Arterial plasma insulin in diabetic groups was reduced by about one-half (P < 0.05) compared with nondiabetic groups. Soleus and gastrocnemius-plantaris complex muscle wet weights were lower because of diabetes, but in response to chronic exercise these muscles hypertrophied in diabetic (0.028 +/- 0.003 vs. 0.032 +/- 0.0015 g/cm for sedentary vs. exercised soleus and 0.42 +/- 0.068 vs. 0.53 +/- 0.041 g/cm for sedentary vs. exercised gastrocnemius-plantaris, both P < 0.05) but not in nondiabetic (0.041 +/- 0.0026 vs. 0.042 +/- 0.003 g/cm for sedentary vs. exercised soleus and 0.72 +/- 0.015 vs. 0.69 +/- 0.013 g/cm for sedentary vs. exercised gastrocnemius-plantaris) rats when muscle weight was expressed relative to tibial length or body weight (data not shown). Another group of diabetic rats that lifted heavier weights showed muscle hypertrophy. Rates of protein synthesis were higher in red gastrocnemius in chronically exercised than in sedentary rats: 155 +/- 11 and 170 +/- 7 nmol phenylalanine incorporated x g muscle(-1) x h(-1) in exercised diabetic and nondiabetic rats vs. 110 +/- 14 and 143 +/- 7 nmol phenylalanine incorporated x g muscle(-1) x h(-1) in sedentary diabetic and nondiabetic rats. These elevations, however, were lower than in acutely exercised (but untrained) rats: 176 +/- 15 and 193 +/- 8 nmol phenylalanine incorporated x g muscle(-1) x h(-1) in diabetic and nondiabetic rats. Finally, chronic exercise training in diabetic rats was associated with reductions in basal glycemia, and such reductions did not occur in sedentary diabetic groups. These data demonstrate that, despite lower circulating insulin concentrations, diabetic rats can increase muscle mass in response to a physiological stimulus.

REDUCED SKELETAL MUSCLE MASS IN MODERATELY DIABETIC RATS IS PARTIALLY RESTORED BY RESISTANCE EXERCISE

1302 The purpose of this study was to determine whether muscle hypertrophy occurs in diabetic rats in response to resistance exercise. Male Sprague Dawely rats performed resistance exercise by repeated standing on the hindlimbs with weighted backpacks. Diabetic(partial pancreatectomy) or nondiabetic rats performed progressive resistance exercise for 8 weeks or remained sedentary (sed). Arterial plasma insulin in the diabetic groups were reduced by about half (p<0.05) when compared to the nondiabetic groups. Soleus(sol) and gastrocnemius/plantaris (gast/plant) complex muscle wet weights were lower due to diabetes but in response to chronic exercise these muscles hypertrophied in diabetic(soleus: 0.28±.03 sed vs 0.32±.015 ex; gast/plant 0.42±.068 sed vs 0.53±0.041 ex both p<0.05) but not in nondiabetic (0.41±.026 sed vs 0.42±.03 ex; 0.72±.015 sed vs. .069±.013 ex) rats when muscle weight was expressed relative to tibial length(g·cm−1) or body weight(data not shown). Rates of protein synthesis (measured using the in vivo phenylalanine flooding dose technique) were higher in red gastrocnemius of both chronically exercised diabetic(155±11 nmol phenylalanine incorporated/ g muscle / hr) and nondiabetic(170±7) rats compared to sedentary diabetic(110±14) and nondiabetic(143±7). Chronic exercise training was associated with reductions in basal glycemia and such reductions did not occur in sedentary diabetic groups. These data demonstrate that moderately diabetic rats can hypertrophy muscle in response to a physiological stimulus. Support by NIH grants: AR43127, GM39277, DK15658

Standard Weight (Ws) Equation and Length Categories for Shovelnose Sturgeon

Abstract Weight–length data were compiled from 32 populations of shovelnose sturgeon Scaphirhynchus platorynchus (N = 11,820) from nine states within the geographic distribution of the species. We used the regression-line-percentile technique, which provides a 75th-percentile standard, to develop the standard weight (Ws ) equation. The proposed equation in metric units is log10 Ws = −6.287 + 3.330 log10FL; Ws is weight in grams and FL is fork length in millimeters. The equivalent equation in English units is log10 Ws = −4.266 + 3.330 log10FL; Ws is weight in pounds and FL is fork length in inches. These equations are proposed for use with shovelnose sturgeon between 120 mm (5 in) and 1,050 mm (41 in). Values for relative weight (Wr ) calculated with the Ws equation did not consistently increase or decrease with increasing fish length, indicating absence of length bias. We propose the following length categories for calculation of proportional stock density (PSD) and relative stock densities (RSDs): stock,...

A Standard Weight Equation to Assess the Condition of North American Lake Herring (Coregonus artedi)

We developed a 75th-percentile standard weight (Ws) equation to aid in the analysis of lake herring (Coregonus artedi) body condition over temporal periods and across populations. Weight-length data were obtained for 23,115 lake herring from 61 North American populations. The proposed equation is log10 Ws = −5.517 + 3.224 log10 TL, where Ws is the standard weight in grams and TL is the maximum total length in millimeters. The equation is valid for lake herring ≥ 100 mm and allows calculation of the relative weight (Wr) index. Significantly lower (P<0.001) Wr values were present for Lake Superior lake herring populations than for the “inland” populations, suggesting that Lake Superior herring weigh less at a given length. Based on the world record lake herring length (55.9 cm), we propose minimum standardized length categories of 13,20,28,35, and 43 cm for stock, quality, preferred, memorable, and trophy lengths, respectively. The length categories facilitate analysis across length groups and the calculation of stock density indices.

Standard Weight Equation for Tiger Muskellunge (Esox lucius x Esox masquinongy)

ABSTRACT Weight and length data for tiger muskellunge Esox lucius x Esox masquinongy were solicited from biologists across the continent to develop a 75th-percentile standard weight (W s ) equation for the hybrid. Only 27 populations (N = 1,124 fish) from 9 states yielded adequate data sets for this process. We used a bootstrap technique to demonstrate that the limited number of populations used was adequate to develop a reliable standard weight equation. Sample variance of slopes was less than 0.002 and bias was minimal with only 19 populations. The standard weight relationship was derived with the regression-line-percentile technique applied to fish over 240 mm (approximately 10 in). The proposed equation is log10 W s = −6.126 + 3.337log10TL, where W s is the weight in grams and TL is the total length in millimeters. The English equivalent (pounds and inches) is log10 W s = −4.095 + 3.337log10TL. No regional trends in the slopes of the log transformed weight-length data were observed. Fish from western populations however, tended to be plumper than their eastern counterparts.

Relative Weight as a Body Condition Index for Chain Pickerel

ABSTRACT Weight-length data from 115 chain pickerel Esox niger populations from 13 states and one Canadian province were used to develop a standard weight (Ws) equation that would allow calculation of relative weight (Wr) values. We developed the 75th-percentile Ws equation using the regression-line-percentile (RLP) method. The proposed Ws equation is log10 Ws(g) = −5.824 + 3.243 log10total length (TL; mm). The English equivalent of this equation is log10 Ws(lb) = −3.293 + 3.243 log10TL(in). The equation is useful for 150 mm and longer chain pickerel. We found no evidence of consistent trends of increasing or decreasing Wr values calculated with the proposed RLP Ws equation. We recommend the use of the proposed RLP Ws equation for assessment of chain pickerel body condition. The proposed Ws equation should serve as a basis for further evaluation of Wr as an index to growth and other physiological trends for chain pickerel.