Striped Bass Stocks Research Articles

Quantifying the Effects of Aging Bias in Atlantic Striped Bass Stock Assessment

AbstractThe effects of aging bias on stock assessment have been evaluated in many simulation studies. However, simulated data cannot be used to quantify the magnitude of aging biases in a real data set and thus their effects on an ongoing stock assessment. In this study, we validated scale and otolith aging using Striped Bass Morone saxatilis of known age collected from the Chesapeake Bay between 1997 and 2006. Otoliths provided more accurate (74% agreement) and precise (average CV = 1.9%) age estimates than scales, which overestimated the ages of young fish and underestimated the ages of old fish (22% agreement; average CV = 9.8%). Based on their accuracy, otolith ages were subsequently used to quantify aging biases in the scale ages and effects of bias in the stock assessment of Atlantic Striped Bass. We converted scale‐age to otolith‐age input using paired scale and otolith ages of Striped Bass collected by commercial fisheries in Virginia waters of the Chesapeake Bay and the mid‐Atlantic from 1999 to 2010. A statistical catch‐at‐age model was run with the scale‐ and otolith‐age input data and the results were compared. We found that aging biases from scale ages resulted in underestimates of population abundance (15%) and female spawning stock biomass (19%) and overestimates of fishing mortality in the terminal year (19%) and made strong age‐1 recruitment years appear weaker and weak ones stronger. Our study demonstrates how aging bias in a large scale‐age sample can be corrected with a relatively small sample of paired scale–otolith ages and provides fisheries management with a quantitative evaluation of aging bias and its effects on the assessment of the Atlantic Striped Bass stock.

Hatchery programs, stock enhancement, and cost effectiveness: A case study of the Albemarle Sound/Roanoke River stocking program 1981–1996

Abstract Fish hatchery programs commonly are used to enhance depleted fish populations. While these programs are highly valued by the public, most likely due to their nonrestrictive approach to restoring a fishery, the effectiveness of these programs has been often questioned. This study investigates economic and ecological effectiveness of the Albemarle Sound/Roanoke River (AR) striped bass stocking program from 1981 to1996 as a case study.

A Model Analysis of Strategies for Enhancing Stocking Success of Landlocked Striped Bass Populations

Abstract Poor first-year winter survival of stocked fingerling striped bass Morone saxatilis, resulting from slow summer growth and small body size in the fall, has limited the sport fishery of Smith Mountain Lake, Virginia. We used an individual-based model to examine different strategies for improving the success of the striped bass stocking program. For two spatially explicit compartments (littoral and pelagic zones) assigned for Smith Mountain Lake, the model simulates daily movement, consumption, growth, and mortality of juvenile striped bass from the time of stocking in early summer until 1 May of the next year. Model predictions of fish prey consumption, predator–prey size relationships, first-year survival, and fall versus spring length-frequency distributions were similar to observed data. Simulations were conducted to examine the effects of fingerling size, stocking density, and day of year at introduction on first-year growth, survival, and recruitment to age 1 and to determine the sensitivity ...

Variation in Larval Growth Rate among Striped Bass Stocks from Different Latitudes

Field observations of a variety of fish species at different latitudes suggest that there is an inverse (countergradient) relationship between growth rate within the first growing season and the length of the growing season. In this study, larvae of striped bass Morone saxatilis from four different latitudes—Hudson River, New York (NY) (41°N); Nanticoke and Patuxent rivers, Maryland (MD) (38°N); Santee–Cooper river system, South Carolina (SC) (33°N); Apalachicola River, Florida (FL) (30°N)—were raised in captivity under identical conditions to determine if differences in growth could be detected among the populations. Larvae from two mothers per latitude were reared at two temperatures (17°C and 21°C) with replication. The general result was that MD and NY larvae exhibited the highest growth rates and SC larvae grew the slowest. At 17°C, a significant difference in standard length growth rate was detected between MD larvae, the fastest growing population, and SC larvae, the slowest growing population. At 21°C, the rank order for growth in standard length was MD = NY > FL = SC. No significant differences in dry weight growth were found at 17°C. At 21°C, a significant difference in dry weight growth rate was detected between NY larvae—the fastest growing population—and SC larvae—the slowest growing population. Significant differences among the populations also were found in egg weight and egg oil volume. However, these maternal effects did not exert a statistically significant influence on growth rate. Results indicate the existence of a countergradient relationship between larval growth rate and the length of the growing season among striped bass from different latitudes.

Comment: Mitochondrial DNA Stability and Striped Bass Stock Identification

Comment: Mitochondrial DNA Stability and Striped Bass Stock Identification

Use of Mitochondrial DNA Polymorphisms to Estimate the Relative Contributions of the Hudson River and Chesapeake Bay Striped Bass Stocks to the Mixed Fishery on the Atlantic Coast

Restriction fragment length polymorphism (RFLP) analysis of mitochondrial DNA (mtDNA) was used to characterize stocks of striped bass Morone saxatilis and to estimate their relative contributions during the fall of 1989 to the mixed coastal fishery at eastern Long Island, New York. Mitochondrial DNA was obtained from reference samples of striped bass collected during the spring of 1989 from the Hudson River, New York, and four spawning areas of the Chesapeake Bay (Choptank, Rappahannock, and Potomac rivers and the upper Chesapeake Bay). Five mtDNA major length genotypes were detected in these fish, and significant differences in their frequencies were observed between the Hudson River and Chesapeake Bay samples. An mtDNA minor length genotype found in some fish (13%) from the Chesapeake Bay and absent from all Hudson River samples provided a second discriminatory character. By using a constrained generalized least squares approach, we estimated that the Hudson River and Chesapeake Bay stocks contributed 73% (95% confidence interval 50–87%) and 27% (95% confidence interval 13–51 %) respectively, of the mixed fishery sample. The probability of the Hudson River contribution exceeding the Chesapeake Bay contribution in this sample was more than 95%. These results suggest that the Hudson River contribution to the mixed coastal fishery was greater in 1989 than reported in earlier studies. We also found no differences in mtDNA major length genotype frequencies among as many as 11 year-classes within the Hudson River, Chesapeake Bay, or Roanoke River spawning systems. These results indicate that mtDNA RFLP genotypes in these striped bass stocks are temporally stable within a fisheries context. An advantage to mtDNA analysis over phenotypic approaches is that, because mtDNA genotype frequencies are not subject to environmentally induced variation, efforts subsequent to an initial survey can focus on characterizing the mixed coastal fishery.

Discrimination of Striped Bass Stocks: A New Method Based on Chemometry of the Fatty Acid Profile in Heart Tissue

Abstract The composition of fatty acids in the tissue of hearts of striped bass Morone saxatilis was determined by a chemometric method, consisting of methanolysis of the tissue, gas chromatography of the resulting fatty acid methyl esters, and multivariate statistical treatment of the analytical data. Striped bass from spawning stocks in the Hudson River, the Roanoke River, and the Chesapeake Bay area had significantly different profiles of 13 selected fatty acids, although the spread among individuals within stocks was considerable, In a training set of 49 striped bass, all were correctly classified; in a test set of 19 samples, 84% were assigned to the correct stock.

Striped Bass Stocks and Concentrations of Polychlorinated Biphenyls

Harvest restrictions on striped bass Morone saxatilis fisheries in Atlantic coastal states were relaxed in 1990, but consistent, coastwide regulations of the harvest have been difficult to implement because of the mixed-stock nature of the fisheries and the recognized contamination of Hudson River fish by polychlorinated biphenyls (PCBs). We examined PCB concentrations and stock of origin of coastal striped bass to better understand the effects of these two factors on the composition of the harvest. The probability of observing differences in PCB concentration among fish from the Hudson River stock and the “southern” group (Chesapeake Bay and Roanoke River stocks combined) was investigated with the logit model (a linear model for analysis of categorical data). Although total PCB concentrations were highly variable among fish from the two groups, striped bass classified as Hudson River stock had a significantly greater probability of having PCB concentrations equal to or greater than 2.00 mg/kg than did fish belonging to the southern group for all age- and size-classes examined. There was a significantly greater probability of observing total PCB concentrations equal to or exceeding 2.00 mg/kg in fish that were 5, 6, and 7 or more years old, and this probability increased linearly with age, We observed similar results when we examined the effect of size on total PCB concentration. The minimum-size limit estimated to permit escapement of fish to sustain stock production is 610 mm total length. Unless total PCB concentrations decrease in striped bass, it is likely that many harvestable fish will have concentrations that exceed the tolerance limit set by the U.S. Food and Drug Administration.

Rise and Fall of the Potomac River Striped Bass Stock: A Hypothesis of the Role of Sewage

Abstract The spawning and nursery area of striped bass Morone saxatilis in the Potomac River is located about 30 km downstream from the outfall of the Blue Plains sewage treatment plant in Washington, D.C. The area coincides with the fertile zone of the river that receives sewage from several treatment plants and has abundant phytoplankton and zooplankton. During the striped bass spawning season, April to June, there is a longitudinal downriver succession of sewage nutrients, phytoplankton, zooplankton, and striped bass larvae, suggesting the presence of a trophic link between sewage nutrients and larvae. We developed a transfer function-noise model of average daily biological oxygen demand loadings from sewage treatment plants and the total commercial landings of striped bass from 1938 to 1983. The model suggests a causal relationship between the sewage nutrients and the fishery. A multiplicative decomposition analysis of striped bass juvenile indices from 1958 to 1986 suggests that sewage nutrients play...

Immunological Discrimination of Atlantic Striped Bass Stocks

Abstract Stocks of Atlantic striped bass Morone saxatilis that were assumed to be geographically isolated during spawning showed strong antigenic differences in blood serum albumin. A discriminant function was estimated from the immunologic responses of northern (Canadian and Hudson River) and southern (Chesapeake Bay and Roanoke River) stocks to two reference antisera. The function correctly classified 92% of the northern and 95% of the southern fish in the training set. Cross-validation revealed similar percentages of correct classification for fish that were of known origin but not used to estimate the discriminant function. Monte Carlo experiments were used to evaluate the ability of the discriminant function to predict the relative contribution of northern fish in samples of various size and stock composition. Averages of predicted proportions of northern fish in the samples agreed well with actual proportions. Coefficients of variation (100 × SD/mean) in the predicted proportions ranged from 1.5 to ...

Contribution of Chesapeake Bay and Hudson River Stocks of Striped Bass to Rhode Island Coastal Waters as Estimated by Isoelectric Focusing of Eye Lens Proteins

Abstract The stock structure of the exploitable population of striped bass Morone saxatilis in Rhode Island coastal waters was estimated by a quadratic discriminant analysis of nine proteins of eye lenses separated by isoelectric focusing. This technique permitted identification of Hudson River and Chesapeake Bay striped bass with 88.0 and 89.5% correct classification, respectively. Classification of individuals sampled from the Rhode Island commercial trap-net fishery in November 1982 indicated that approximately 54% were from the Chesapeake Bay stock and 46% were from the Hudson River stock. These stock composition estimates apply to age-2–5 striped bass from the exploitable population in Rhode Island. The stock composition of the coastal population is expected to change with time and with relative year-class strengths of the contributing stocks.

Electrophoretic Analysis of Genetic Variability in a Landlocked Striped Bass Population

Abstract Isozyme electrophoresis was used to assess biochemical genetic variation in spawning striped bass Morone saxatilis captured from two tributaries of Kerr Reservoir, Virginia-North Carolina in 1979 and 1980. Only 3 of 56 scorable loci were polymorphic. Average heterozygosity was estimated at 1.6%, similar to measurements made on anadromous Atlantic coast striped bass stocks, but well below typical values for either freshwater or marine fish species. Allele frequencies of polymorphic loci were independent of sex and age, with the exception of Itp, which demonstrated variation among age groups. Allele frequencies for each of the polymorphic loci differed significantly between rivers for collections made in 1979 but not in 1980. It is hypothesized that striped bass exhibit spatial as well as temporal heterogeneity in the distribution of genotypes within spawning rivers, which can influence interpretation of genetic distinctness of spawning groups. The low degree of genetic variability which is resolva...

Recognition of Year-Class Dominance in Striped Bass Management

Abstract Major biological processes that establish the year-class strengths of Atlantic coast striped bass stocks (Morone saxatilis) are reviewed. Environmental factors seem to be the most important determinants of the initial population sizes. A general management strategy is proposed, which is consistent with the environmentally controlled occurrences of dominant year classes, and which also optimizes benefits from the fisheries. Because the relative importance of biological and abiotic population controls is uncertain, the proposed management strategy also strives to protect the reproductive potential of the striped bass stocks. This biologically based strategy can be implemented in the form of regulations that are flexible temporally and geographically.

On the Proportion of the Chesapeake Bay Stock of Striped Bass That Migrates into the Coastal Fishery

Past observations of year-class patterns and racial characteristics of striped bass (Morone saxatilis) indicate that the Chesapeake Bay spawning grounds provide the principal support of the Atlantic coastal fishery for this species. Past tagging studies have suggested that only a few percent of the striped bass leave the bay, but a few percent of the Chesapeake Bay stock could not support the coastal fishery. To resolve this contradiction, I reexamined tagging studies conducted during 1957–1961 in the Potomac River using recent data on age-specific sex ratios at several positions in the river. For 3-year-olds, the proportions of tag returns from outside the bay were linearly related to the female proportion of the stock in the tagging area. The analysis indicates that few young males leave the bay and approximately one-half of the 3-year-old females migrate to coastal waters. A similar estimate that 50% of age-III females migrate from the bay was independently derived from age-specific sex ratios in Chesapeake Bay in fall 1976, coupled with sex-specific estimates of spring fishing mortality. Smaller proportions of age-II and age-IV females leave the bay. This level of migration could support the majority of the coastal striped bass fishery.