Biology and Management of Inland Striped Bass and Hybrid Striped Bass

<em>Abstract</em>.—We compared the habitat selection (temperature and dissolved oxygen) of striped bass (STB) <em>Morone saxatilis</em> and hybrid striped bass (HSB; palmetto bass [male white bass <em>M. chrysops</em> × female striped bass]) in Claytor Lake, Virginia. Striped bass (<em>n </em>= 28) and HSB (<em>n </em>= 33) were implanted with temperature-sensitive radio tags and tracked biweekly for a period of 19 months to record position and habitat use. Striped bass averaged 715 mm total length (range 533–940) whereas HSB averaged 547 mm total length (range 460–659). Habitat separation was most apparent in the warm season months of June through August. During this period, when deoxygenation of the metalimnion and hypolimnion was not limiting, STB and HSB segregated according to apparent temperature preferences, with HSB selecting warmer temperatures. As deoxygenation progressed, HSB and especially STB were forced into warmer strata than preferred. Results from this study suggest that if favorable dissolved oxygen levels are maintained, STB and HSB will vertically segregate during summer stratification. Temperature selection and qualitative observations of fish mortality in summer indicated that adult HSB would be less vulnerable than adult STB to a temperature–dissolved oxygen squeeze in summer and its detrimental effects.

Biology and Management of Inland Striped Bass and Hybrid Striped Bass

<em>Abstract</em>.—Much is known about the biology and management of striped bass <em>Morone saxatilis</em> and its hybrids, but much information is still needed for more effective management. Researchers are closing in on a grand unified theory of habitat selection by striped bass as a function of their size, thermal ecology, dissolved oxygen requirements, and forage availability. The role of forage in influencing habitat selection is perhaps the least understood and deserves further scrutiny to better predict the quality of striped bass fisheries. Although we can measure and model physico-chemical habitat quality, modeling habitat selection by striped bass is challenging, in part because systems vary widely in their physico-chemical and biological characteristics. Managing striped bass in some western U.S. waters, where natural reproduction can produce too many recruits, may become more challenging as reservoirs age and traditional fisheries for black basses <em>Micropterus</em> spp. decline. Modeling the population dynamics of striped bass and hybrid striped bass is simplified by the fact that most fisheries are maintained by stocking programs and the initial number of juvenile recruits is known with certainty; however, sampling protocols that will consistently yield unbiased estimates of key population parameters are needed. The potential for disruptive controversies surrounding striped bass management will always exist; however, increased use of conflict resolution techniques will help limit the collateral damage that often accompanies such controversies. Estimates of the benefits and costs associated with maintaining moronid fisheries are scarce but could ease such conflicts and help justify stocking programs. While inland striped bass and hybrid striped bass fisheries remain popular and are the focus of much management activity, the outlook for native stocks of striped bass in the Gulf of Mexico drainage is of concern. The state of knowledge concerning hybrid striped bass ecology and management is decades behind what we know about striped bass ecology and management. This situation needs to be addressed if agencies expand their hybrid striped bass stocking programs in response to changing reservoir environments, as some agencies in the southeast United States have already done.

Biology and Management of Inland Striped Bass and Hybrid Striped Bass

<em>Abstract</em>.—Competitive interactions among reservoir fishes may be pronounced because fish assemblages in these artificial environments have had little time to develop niche-partitioning strategies that alleviate negative interspecific interactions. Such interactions may at times have been intensified by introductions of predators such as striped bass <em>Morone saxatilis</em>, introduced to create additional fisheries and control pelagic clupeids. Possible interactions between existing fish assemblages and striped bass include predation and competition. While there is a perception among angler groups that predation by striped bass on coexisting game fish is significant, most studies have reported little or no predation on game fish by striped bass and have considered predation rare and inconsequential. Moreover, predation that occurs will likely be compensatory and fail to reduce overall game fish survival. Any indirect effect of striped bass predation by restricting prey-sized game fish to limited refuge sites remains unknown. Exploitative competition may be more common. Although infrequently, introduced striped bass have depleted prey resources shared with other piscivores, particularly when stocking rates have been high, when there is a high rate of natural reproduction, or when prey supply has plunged in response to environmental fluxes. Fluctuation in prey supply, associated with ordinary environmental variability, and associated time lags in prey supply and predator demand, preclude adjusting predator densities to exactly balance demand with supply. The frequency of low supply–demand ratios varies across systems and exhibits seasonal trends. Nevertheless, chronic supply–demand imbalances are manageable where the predator assemblage is at least partially controlled through stocking, harvest regulations, or both. Because of the poor state of knowledge concerning the parameters defining balance and because uncontrollable annual fluctuations preclude exact management of alternating prey levels, we suggest adjusting stocking to manage demand so that it equals the median historical prey supply. Simulating the removal of striped bass and predicting the aftermath may be the most cost-effective way to provide decision support for stakeholders involved in determining if a striped bass stocking program is beneficial to most users.

Biology and Management of Inland Striped Bass and Hybrid Striped Bass

<em>Abstract</em>.—Inland populations of striped bass <em>Morone saxatilis </em>and hybrid striped bass (white bass <em>M. chrysops </em>× striped bass) are intensively managed across the United States for their recreational value using a variety of regulations; however, the full extent of different regulatory strategies is unknown. This paper describes regulations used by states to manage their inland striped bass and hybrid striped bass fisheries. An Internet-based survey seeking information on issues such as stocking dependency, trophy potential, catch rates, and statewide and specialized regulations for both striped bass and hybrid striped bass fisheries was created and distributed to all state agencies. The survey found that 32 states have inland populations of striped bass, hybrid striped bass, or both. Daily creel limits for striped bass and hybrid striped bass ranged from 2 to 30; the most liberal creel limits were found in southern states. Half of the states reported that their statewide length limit for both taxa has few or no exceptions for conditions in particular water bodies, and 85% of states with striped bass and 92% of states with hybrid striped bass enforce a minimum length limit as their statewide length limit. Although both taxa were generally managed with similar regulations, striped bass were usually considered a more important sport fish species and were managed more intensively than hybrid striped bass. A literature review confirmed that little research has been published on the response (or lack thereof) of striped bass and their hybrids to any of the various management schemes reported herein.

Biology and Management of Inland Striped Bass and Hybrid Striped Bass

<em>Abstract</em>.—The emerging use of genetic markers for stock identification is advantageous as this technique utilizes an inherent permanent mark, it eliminates stress associated with conventional tagging methods, and mark recovery is nonlethal. In controlled experiments, increased accuracy and reliability have been demonstrated with genetic tags, as compared to other commonly used markers. While a variety of genetic markers exist for fish identification, microsatellites are preferred because of their polymorphic nature and versatile use, including identification of population structure, measures of genetic diversity, and parentage analysis. Microsatellites provide a cost-effective tool for a variety of applications, including their use in complex experimental designs, as well as responsible genetic population management. We provide examples of the use of microsatellites as genetic tags in South Carolina striped bass <em>Morone saxatilis</em>, describing an experimental restoration effort in the Ashley River and a large-scale stock enhancement effort for the Santee-Cooper reservoirs.

Biology and Management of Inland Striped Bass and Hybrid Striped Bass

<em>Abstract</em>.—The stocking of fingerling striped bass <em>Morone saxatilis</em> in freshwater impoundments has led to the development of successful put-grow-take fisheries throughout the southern United States. However, first-year survival of stocked fingerlings is often low. To enhance stocking success of striped bass, a better understanding is needed on the impacts of different stocking strategies on early life-history dynamics. In this review paper, we first examined the existing literature on the role of abiotic and biotic factors on recruitment dynamics of stocked piscivores in inland freshwater systems. Second, we compiled the results of a progressive series of studies that were completed over a 25-year period in Smith Mountain Lake, Virginia, that focused on understanding the relationship between striped bass stocking success and biotic interactions, forage-fish prey availability and dynamics, and first-year recruitment. This case study demonstrated that differential intra-cohort growth and poor first-year winter survival are the primary factors limiting stocking success and that stocking fingerlings at a greater number of sites throughout the lake at lower densities improved recruitment to age 1. With this information, we provide stocking size, time, density, and location strategy recommendations that should yield increased survival and stocking success of striped bass in freshwater impoundments.

Biology and Management of Inland Striped Bass and Hybrid Striped Bass

<em>Abstract</em>.—Population models are frequently used to assess stocks and inform management, but use of models for inland striped bass <em>Morone saxatilis</em> fisheries is rare in the literature. We summarize three common types of population models and describe how they could aid management of striped bass and hybrid striped bass fisheries. Yield-per-recruit models are ideal for identifying growth overfishing and optimum size at harvest to maximize yield. Time-dynamic, age-structured models are useful for evaluating effects of variable recruitment on angler catch and effects of temporary changes in model parameters (e.g., fish kills, changes in growth) on model output. Catch-at-age models can be used to measure recruitment to age 1 for inland striped bass fisheries and for quantifying fishing mortality rates. Catch-at-age models can also improve the utility of creel survey data and help evaluate the efficacy of stocking programs by estimating age-1 recruits (from model) per stocked fish (from hatchery). Population models force investigators to be explicit about their hypotheses regarding fisheries systems, identify data gaps, and allow assessment of potential impacts of management actions on the fishery. The examples shown here can be used to improve striped bass and hybrid striped bass monitoring and management.

Biology and Management of Inland Striped Bass and Hybrid Striped Bass

<em>Abstract</em>.—A CE-QUAL-W2 water quality model was used to characterize the availability of striped bass <em>Morone saxatilis</em> habitat in Lake Greenwood, South Carolina, during 2004 and 2005. Although the lake has a productive fishery, water quality and aquatic habitat are affected by nutrient loading, algal blooms, and extensive oxygen depletion in the bottom waters. The main objectives were to characterize habitat availability and predict the implications of a change in phosphorus loading from the Saluda and Reedy rivers. The baseline scenario of the model showed that habitat was most critical during July and August, when as little of 5% of the reservoir contained tolerable habitat (temperature <28°C and dissolved oxygen >2 mg/L). Favorable habitat (temperature <25°C and dissolved oxygen >2 mg/L) was usually absent for most of July and August. Pulses of higher inflow or freshets produced short-term increases in tolerable habitat, especially in the upper end of the reservoir. Phosphorus-loading scenarios predicted that large reductions (50% or more) would be required to improve habitat substantially during midsummer. For the manager of a striped bass fishery, water quality models can be useful tools for evaluating habitat, especially under marginal conditions, and for predicting the impact of altered water management practices.

Biology and Management of Inland Striped Bass and Hybrid Striped Bass

<em>Abstract</em>.—Striped bass <em>Morone saxatilis</em>, originally a coastal and estuarine species, has been introduced in reservoirs in the southeastern and western United States. Although such stocking established many successful fisheries, there were troublesome die-offs of adult striped bass (3–9 kg, generally >5 kg) in some waters, usually in late summer. In contrast, juveniles and small adults thrived. In response to these patterns, my students and I conducted several years of telemetry studies of adult striped bass, primarily in Cherokee and Watts Bar reservoirs, Tennessee, and laboratory studies of juvenile temperature selection. In 1985, I published the “temperature–oxygen squeeze” hypothesis to explain mortalities of large fish on the basis of limited availability of cool (<25°C), oxygenated (>2 mg/L) water in summer while juveniles successfully occupied a warmer thermal niche (>25°C). We now have more than 20 years of research and management since 1985, primarily across the Southeast, in which the published hypothesis has, explicitly or not, been tested, generally confirmed, and applied to management. This retrospective paper reviews the studies our team conducted to develop and test the hypothesis and about 20 years of relevant studies by others that have added important nuances, addressed lingering issues, and turned a controversial idea into generally accepted understanding and management practice. Nonetheless, issues remain for understanding the effects of poor summer habitat on striped bass, such as why some studies show striped bass occupying warmer temperatures without mortalities and the role of prey availability in survival of fish obliged to occupy warm water. Other papers in this volume augment and extend the saga of progressively developing knowledge that this paper recalls of striped bass habitat requirements, thermal niche segregation by size (or age), and management constraints and opportunities.