Kenneth G. Ostrand

Physiological and Behavioral Consequences of Long‐Term Artificial Selection for Vulnerability to Recreational Angling in a Teleost Fish

Few studies have examined the physiological and behavioral consequences of fisheries‐induced selection. We evaluated how four generations of artificial truncation selection for vulnerability to recreational angling (i.e., stocks selected for high and low vulnerability [HVF and LVF, respectively]) affected cardiovascular physiology and parental care behavior in the teleost fish largemouth bass Micropterus salmoides. Where possible, we compared artificially selected fish to control fish (CF) collected from the wild. Although, compared to control fish, resting cardiac activity was ∼18% lower for LVF and ∼20% higher for HVF, maximal values did not vary among treatments. As a result, the HVF had less cardiac scope than either LVF or CF. Recovery rates after exercise were similar for HVF and CF but slower for LVF. When engaged in parental care activities, nesting male HVF were captured more easily than male LVF. During parental care, HVF also had higher turning rates and pectoral and caudal fin beat rates, increased vigilance against predators, and higher in situ swimming speeds. Energetics simulations indicated that to achieve the same level of growth, the disparity in metabolic rates would require HVF to consume approximately 40% more food than LVF. Selection for angling vulnerability resulted in clear differences in physiological and energetic attributes. Not only is vulnerability to angling a heritable trait, but high vulnerability covaries with factors including higher metabolic rates, reduced metabolic scope, and increased parental care activity. Despite these energetically costly differences, HVF and LVF of the same age were of similar size, suggesting that heightened food consumption in HVF compensated for added costs in experimental ponds. Ultimately, angling vulnerability appears to be a complex interaction of numerous factors leading to selection for very different phenotypes. If HVF are selectively harvested from a population, the remaining fish in that population may be less effective in providing parental care, potentially reducing reproductive output. The strong angling pressure in many freshwater systems, and therefore the potential for this to occur in the wild, necessitate management approaches that recognize the potential evolutionary consequences of angling.

ENERGETICS, PREDATION, AND RATION AFFECT SIZE‐DEPENDENT GROWTH AND MORTALITY OF FISH DURING WINTER

Winter temperatures may reduce energy costs for ectotherms. However, variable mid-temperate and low-latitude winters may interact with scaling of size, metabolism, and energy reserves to cause energy deficits and require trade-offs between foraging and predation. A dynamic optimization model explored how ration, fall fat, and both non- and size-selective predation influenced foraging (i.e., fast or forage) and energy allocation (i.e., length or fat) decisions that maximize winter survival of age-0 largemouth bass (Micropterus salmoides). During a mid-latitude (38° N) winter, a pond experiment in which age-0 fish occurred with or without adult conspecific predators tested a subset of the model. In the model without predators, winter foraging occurred, with small size only reducing survival when low ration and low fall fat caused small fish to exhaust reserves. With predation, all sizes foraged to maintain mass and fat reserves when ration was sufficiently high, with small fish also growing in length. When modeled predation was nonselective, size-dependent mortality varied in complex ways. In contrast, size-selective predators consistently reduced survival of small fish. Generally consistent with the model, fish in ponds without predators gained mass and energy content, while those with predators only maintained these parameters. All small individuals grew more than large counterparts in length. Mortality in ponds never depended on size but was ∼20% higher with predators. Energy deficits often demand active foraging during mid-temperate winters, with predation rather than energy depletion influencing size-dependent survival.

Injury and Mortality Induced by Four Hook Types on Bluegill and Pumpkinseed

Abstract Tackle manufacturers have responded to concerns regarding hooking injury and mortality by attempting to design and market hooks that are less damaging to fish (e.g., circle hooks). To date, studies investigating circle hooks have been primarily restricted to large marine species. We compared the injury and short-term (72-h) mortality of bluegills Lepomis macrochirus and pumpkinseeds L. gibbosus angled using number-6 circle hooks and three other conventional hook types (aberdeen, wide-gap, and baitholder) across three water temperatures (18, 22, and 26°C). Unlike other hook types, circle hooks were never lodged in the gullet, but they were frequently lodged in the eye. Some fish captured on conventional hooks were hooked deeply in the gullet, necessitating line cutting for release. Incidences of bleeding were low using all hook types, and when not lodged in the gullet, all hooks were generally easy to remove. Anatomical hooking locations differed among small ( 145-mm) bluegills...

Effects of Stress on Largemouth Bass Reproduction

Abstract Although largemouth bass Micropterus salmoides are frequently subjected to sublethal stressors (e.g., angling), the associated effects on their reproductive success have not been assessed. We examined the reproduction of largemouth bass that were subjected to the stress of exhaustive exercise, air exposure, culling, live-well conditions, and weigh-in procedures. Age-0 largemouth bass produced from parents subjected to stress were smaller (total length, 31 ± 0.4 mm (mean ± SE)) and weighed less (0.59 ± 0.04 g) than controls that were not stressed (35 ± 0.4 mm; 0.76 ± 0.03 g). Adults that were stressed had offspring with later swim-up dates than did controls. Our results provide evidence that stress before spawning has the potential to negatively affect largemouth bass reproductive success.

Injury rates, hooking efficiency and mortality potential of largemouth bass (Micropterus salmoides) captured on circle hooks and octopus hooks

Abstract We compared the injury rates, hooking efficiency, and mortality potential of circle hooks and the more conventional octopus hooks for largemouth bass (Micropterus salmoides) captured on minnows in central Illinois. Fish captured on circle hooks (N=125) were hooked less deeply, exhibited less bleeding, and were more easily removed from the hook than were those captured on octopus hooks (N=134). The majority of fish captured using both hook types were hooked in the upper lip. Mortality rates were uniformly low for both hook types (circle, 5.1%; octopus, 6.6%). Fish that were identified as potential mortalities were typically hooked deeply in a vital organ or tissue (i.e., heart, gullet, gill arch), exhibited substantial bleeding, and were difficult to remove from the hook. No size-selective trends were noted among hook types, nor were there any differences in total length among mortalities and survivors. Capture efficiency for circle hooks was half that of octopus hooks. Our results suggest that circle hooks do provide some minimal conservation benefits relative to conventional octopus hooks despite having similar mortality rates.

Cardiovascular Responses of Largemouth Bass to Exhaustive Exercise and Brief Air Exposure over a Range of Water Temperatures

Abstract In this study we examined the effects of exhaustive exercise and brief air exposure on the cardiovascular function of largemouth bass Micropterus salmoides at four water temperatures (13, 17, 21, and 25°C). We used Doppler flow probes to monitor cardiac output and its components (i.e., stroke volume and heart rate) while we manually chased fish to exhaustion to simulate angling, exposed them to air for 30 s, and then recorded patterns of recovery. Resting cardiac variables generally increased with increasing water temperature except for stroke volume, which was temperature independent. Fish heart rate became erratic during exercise, and during air exposure fish exhibited severe bradycardia before becoming tachycardic when returned to the water. Maximal change occurred most rapidly for cardiac output (about 5 min). Several minutes later, changes in heart rate (increase) and stroke volume (decrease) simultaneously reached maximal deviations from resting values. Cardiac output and heart rate increas...

Consequences of Vegetation Density and Prey Species on Spotted Gar Foraging

Abstract Adult spotted gar Lepisosteus oculatus are potentially important components of food webs given their predatory habits and high relative abundance. However, few studies have examined their foraging behavior. Therefore, we examined the effects of vegetation density on the foraging success of adult spotted gars preying on bluegill Lepomis macrochirus and fathead minnow Pimephales promelas. Spotted gars use ambush foraging and were more successful capturing fathead minnow than bluegills at all stem densities. Predation success was negatively correlated with stem density for bluegill prey but not for fathead minnow. Although fathead minnow and bluegills shoaled less as stem density increased, bluegills modified their behavior in the presence of a predator by moving lower in the water column at high stem densities, whereas fathead minnow did not. Predatory behaviors were directed at prey within a short distance and near the surface of the water. Foraging of spotted gar, a lie-in-wait predator, was prim...

Comparison and Validation of Nonlethal Techniques for Estimating Condition in Juvenile Salmonids

Abstract Fish proximate composition influences growth, reproduction, and survival and is commonly used to determine physiological condition; however, proximate composition is time-consuming to measure and typically requires a lethal sample that cannot be analyzed in situ. As a result, researchers are increasingly interested in using nonlethal techniques that are quicker and less expensive to estimate proximate body components in fish. Bioelectrical impedance analysis (BIA) and microwave energy meters have been used with success on large-bodied fishes, although no evaluation on small-bodied Pacific salmon Oncorhynchus spp. has been conducted. We evaluated three nonlethal techniques (BIA, energy meter, and condition factor) as predictors of individual body composition (determined through lethal whole-body proximate analysis) in juvenile hatchery steelhead O. mykiss (minimum fork length = 138 mm; minimum wet mass = 24.5 g). The BIA values were positively correlated with measured total body water (R 2 = 0.77)...

Juvenile Steelhead Release Strategies: A Comparison of Volitional- and Forced-Release Practices

Abstract In 2004 and 2005, steelhead (anadromous rainbow trout Oncorhynchus mykiss) reared at Winthrop National Fish Hatchery (Winthrop, Washington) were tagged with passive integrated transponders and subjected to a volitional or forced release. Gill Na+, K+-ATPase (NKA) activity, body size, condition factor (K), travel time, and apparent survival were compared between volitional migrants (VMs), forced-release migrants (FRMs), and volitional-release nonmigrants (VNMs). Gill NKA activity and body size were similar between VNM, VM, and FRM groups, but K varied by date and migrant group. However, by the end of the volitional-release period, all three groups had similar K. The VNMs consistently demonstrated lower apparent survival to McNary Dam on the Columbia River than did the VM and FRM groups, which had three to eight times greater survival than did VNMs. Volitional migrants had higher apparent survival to McNary Dam than did FRMs in 2005; however, apparent survival was similar between the two groups in ...

Morphological, Physiological, and Genetic Techniques for Improving Field Identification of Steelhead, Coastal Cutthroat Trout, and Hybrid Smolts

Abstract In streams with sympatric populations of steelhead Oncorhynchus mykiss and coastal cutthroat trout O. clarkii clarkii (hereafter, cutthroat trout), life history descriptions and smolt production estimates may be hampered by misclassification of hybrids as steelhead or cutthroat trout. Additionally, important morphological and physiological differences between hybrid and non-hybird smolts are often unknown. Therefore, we assessed field classification and created classification models to quantify and reduce misclassification rates among migrating steelhead, cutthroat trout, and hybrid smolts. Field misclassifications of smolts with steelhead or cutthroat trout genotypes were low (1% and 2%, respectively). However, field misclassification of fish with hybrid genotypes was high, with 11% of the hybrids being misclassified as steelhead and 42% of the hybrids being misclassified as cutthroat trout. Hybrid smolts were larger, had lower gill Na+, K+-ATPase activities, and lower condition factors than steelhead but were similar to cutthroat trout smolts in these same measurements. Additionally, statistical classification analyses using morphological traits including subterminal jaw slash intensity, hyoid teeth presence, maxillary length, breaks of pigment along outer margin of adipose fin, condition factor, and migration date improved classification error rates of hybrids from 53% to 21%. In systems with sympatric populations of steelhead and cutthroat trout, we recommend a thorough evaluation of field-based identification methods with genetic techniques to assess the effectiveness of field-based classification in addition to examining important life history differences among steelhead, cutthroat trout, and their hybrids.