Kevin L. Pope

Seasonal Influences on Freshwater Fisheries Sampling Data

Abstract Fisheries managers often assess fish populations using catch per unit effort (CPUE), size and age structure, growth, and condition. For many freshwater fishes and common sampling gears, CPUE, size and age structure, and condition are highest in the spring and fall, while growth commonly is fastest during the summer growing season. However, there are exceptions to these general trends, especially in populations with erratic recruitment, growth, or mortality. At the least, CPUE, size and age structure, growth, and condition of fish should be expected to change with season, given the effects of variable recruitment, growth, and mortality. However, if recruitment, growth, and mortality are relatively stable, seasonal changes in sampling data occur due to changes in fish behavior caused by many factors (e.g., changes in temperature, turbidity, food availability, photoperiod, etc.). However, these patterns of change through the seasons should not necessarily be assumed to be the same for all fish speci...

Nonlethal Methods of Examining Fish Stomach Contents

Several nonlethal methods have been developed to determine the stomach contents of fish, including gastroscopes, tubes, stomach suction, stomach flushing, emetics, forceps, and chronic fistulas. By reviewing the literature on this subject, we found that the effectiveness (ability to remove all stomach contents) of the different methods depends on size, age, species of fish, and the size of the food items in the stomach. Overall, various methods of stomach flushing were the most effective method of recovering stomach items from a variety of fishes. Mechanized pressure appeared to be the most efficient method of stomach flushing for most large fishes. The use of syringes allowed stomach flushing to be performed on most young and small fishes. The use of tubes and stomach suctions, much simpler and less expensive methods than stomach flushing, were nearly as effective for some fishes such as black bass (Micropterus spp.) and salmonids.

Lure-size Restrictions in Recreational Fisheries

Abstract We conducted angling experiments to examine the potential use of lure-size restrictions to effect or reinforce length limits. We used four sizes of lures and five color patterns to assess effects of lure size and color on the number and length of largemouth bass (Micropterussalmoides) captured by angling. There was a significant (F = 12.03; df 1, 177; P = 0.0007) lure-size effect on the total length (TL) of captured largemouth bass. Catch rates of fish ≥305-mm TL ranged from 0 to 0.5 fish per hour and were unrelated to lure size. Lure color pattern had no effect on length of fish captured (F = 1.44; df = 4, 230; P = 0.2320). Angling experiments and results from angling simulations suggest lure-size restrictions can be used to indirectly effect or reinforce minimum-length limits and provide managers with a means to reduce catch of nontarget-size fish.

A caloric-based evaluation of diet indices for largemouth bass

Selection of methods for quantitative description and assessment of food habits is a concern for trophic investigations. We used diet data for largemouth bass Micropterus salmoides, to compare a caloric-based approach with eight diet indices: percent frequency of occurrence, percent total number, percent total weight, mean relative number, mean relative volume, relative importance index, prey-importance index, and mean stomach fullness. Mean caloric contribution of stomach contents for each prey taxon was used as a standard to compare diet indices. Temporal differences in composition and caloric contents of largemouth bass stomach contents were apparent. Most diet indices provided similar assessments when diets were dominated by a single prey type (i.e., gizzard shad during June-October). However, diet indices evaluated provided dissimilar assessments of stomach contents when a variety of prey with differing caloric densities were consumed (e.g., April). Mean stomach fullness and percent by volume were significantly (p < 0.002) correlated (r = 0.94 − 1.00) with mean caloric contribution of largemouth bass stomach contents during all months. Unlike percent by weight, mean stomach fullness accounted for differences in fish size and stomach capacity. Thus, mean stomach fullness by prey type appears to be the most appropriate index when objectives include simplified caloric-based assessments of fish diets.

Differential Relations of Age-0 Black Crappie and Yellow Perch to Climatological Variables in a Natural Lake

ABSTRACT To better understand recruitment processes of black crappie Pomoxis nigromaculatus and yellow perch Perca flavescens in natural lakes, we sampled age-0 fishes during late summer-early fall 1988–1995 in Brant Lake, South Dakota, with a bottom trawl. Age-0 black crappie catch per unit effort (CPUE) was only >5.0/min when yellow perch CPUE was 0.1/min when black crappie CPUE was <5.0/min. We also found that the CPUE for both species was relatively low compared to other South Dakota waters and concluded that the relation between black crappie and yellow perch was probably not simply interspecific competition. Therefore, we assessed climatological variables to help explain this relation. In general, crappie CPUE was negatively correlated with precipitation and positively correlated with mean daily temperature difference and mean wind speed. Conversely, CPUE for perch was positively correlated with precipitation and negatively correlated with mean daily tempe...

Proposed Revision of the Standard Weight (Ws) Equation for Redear Sunfish

ABSTRACT Weight-length data were compiled from 289 redear sunfish Lepomis microlophus populations. We applied the regression-line-percentile (RLP) technique to weight-length data for 150 redear sunfish populations to develop a new 75th-percentile standard weight (Ws) equation. The proposed RLP Ws equation, log10 Ws = −4.968 + 3.119log10TL where Ws is the standard weight in grams and TL is the total length in millimeters, is valid for fish >70 mm TL. The English-unit equivalent, log10Wg = −3.263 + 3.119log10TL where Ws is the standard weight in pounds and TL is the total length in inches, is valid for fish >3 in TL. We used the remaining 139 independent populations to evaluate the current [log10 Ws = −5.164 + 3.227(log10TL)] and RLP Ws equations for any length-related biases. We confirmed that the current Ws equation is length-biased. That is, relative weight (Wr) values significantly decreased with increasing fish length for far more populations (N=45) than they increased (N=7). We tested the proposed RLP...

Oxytetracycline Marking Efficacy for Yellow Perch Fingerlings and Temporal Assays of Tissue Residues

Differentiating between hatchery and naturally reproduced fishes is difficult because of the lack of appropriate marking techniques. Chemical immersion techniques can be a practical method for mass marking juvenile fishes. The objectives of this study were to determine the concentration of oxytetracycli ne (OTC) hydrochloride needed to effectively mark age-0 yellow perch Perca flavescens. to observe the retention lime of the mark, and to measure the persistence of OTC in body tissues. Fish were immersed in 309, 534, and 748 mg OTC/L for 12 h. Initial fish collections were made weekly, and monthly collections began 1 month postmarking for tissue and mark analyses. High-pressure liquid chromatography was used to quantitate OTC residues in tissues; OTC concentrations were undetectable (<0.05 jxg/g) in the edible tissue (muscle) at 110 d postimmersion. Aided by a Nikon Labophot fluorescence microscope, we discerned otolith marks 56 d postimmersion on 100% of the fish treated at 534 and 748 mg/L. Marks were still visible on 100% of the fish treated with 534 and 748 mg/L at 8 months postimmersion.

Fishing for resilience

AbstractManagement approaches that focus on social–ecological systems—systems comprised of ecosystems, landscapes, and humans—are needed to secure the sustainability of inland recreational fisheries without jeopardizing the integrity of the underlying social and ecological components. Resilience management can be useful because it focuses on providing recreational capacity for fishermen under a variety of conditions while assuring that the social–ecological system is not pushed to a critical threshold that would result in a new, undesired system regime. Resilience management is based on a system perspective that accounts for the possible regimes a system could manifest. It aims to enhance system properties that allow continued maintenance of the system in a desired regime in which multiple goods and services, including recreational capacity, are provided. In this forum paper, we provide an overview of the potential of a resilience approach to the management of recreational fisheries and highlight the scie...

Using the internet to understand angler behavior in the information age

ABSTRACT Declining participation in recreational angling is of great concern to fishery managers because fishing license sales are an important revenue source for protection of aquatic resources. This decline is frequently attributed, in part, to increased societal reliance on electronics. Internet use by anglers is increasing and fishery managers may use the Internet as a unique means to increase angler participation. We examined Internet search behavior using Google Insights for Search, a free online tool that summarizes Google searches from 2004 to 2011 to determine (1) trends in Internet search volume for general fishing related terms and (2) the relative usefulness of terms related to angler recruitment programs across the United States. Though search volume declined for general fishing terms (e.g., fishing, fishing guide), search volume increased for social media and recruitment terms (e.g., fishing forum, family fishing) over the 7-year period. We encourage coordinators of recruitment programs to c...

Shrinkage of Inland Silverside Larvae Preserved in Ethanol and Formalin

Length measurements of preserved larval fish are necessary in many types of larval fish surveys. If the fixative causes significant shrinkage, then the pre- served lengths cannot be used to indicate accurate live lengths. The objective of this study was to determine how preservation in two different concentrations of for- malin and ethanol affects the total length of larval inland silversides Menidia beryllina. Larvae were measured (nearest 0.1 mm) and individually fixed in one of four fixative treatments (80% ethanol, 100% ethanol, 5% buffered formalin, and 10% buffered formalin). Fish were remeasured (nearest 0.1 mm) at 15 min; 4 h; and 1, 7, 14, and 21 d after preservation. Most shrinkage occurred within the first day after preservation in all four fixatives. Initial length was positively correlated with absolute shrinkage, but percent shrinkage was not affected by initial length. We found no difference in percent shrinkage between the 80% and 100% ethanol concentrations. The 10% buffered formalin caused more percent shrinkage than 5% buffered formalin. Further- more, ethanol (80% and 100% combined) caused greater percent shrinkage than either 5% or 10% buffered for- malin. Accurate length measurements are necessary in many types of larval fish surveys to determine factors such as age, growth, or size-selective mor- tality. When a large number of fish are collected in the field, it is often necessary to preserve them so they can be analyzed later. If the fixative causes significant shrinkage, then preserved lengths can- not be used to indicate accurate live lengths.