Survey of Intersex (Testicular Oocytes) in Black Crappie Collected from the Illinois River Waterway

Researchers have documented intersex (testicular oocytes) in male fishes in many species worldwide and prevalence of the condition is strongly related to exposure to endocrine-disrupting compounds in aquatic ecosystems. There is no available knowledge about the incidence of intersex in Black Crappie Pomoxis nigromaculatus, an important North American sport fish. The objective of this survey was to investigate the prevalence and distribution of the intersex condition in Black Crappie collected from portions of the Illinois River waterway. We collected and examined 83 Black Crappie. We observed testicular oocytes in 22 individuals (27% intersex), representing the first documentation of intersex condition in wild Black Crappie. The number of oocytes that we observed in intersex Black Crappie ranged from 1 to 67. We documented intersex in individuals collected from all habitats, but there were no significant differences in the prevalence of the condition (Kruskal–Wallis P = 0.56) or the number of oocytes present (P = 0.25) in intersex males from the different habitats. Permutational multivariate analysis of variance indicated that morphometric parameters varied significantly among locations (P = 0.0001), but did not vary significantly between intersex and normal males. We have little information about the current distribution of endocrine-disrupting compounds in the specific regions where we collected Black Crappie for our study. However, we believe our study represents a valuable effort to detect the condition in an important sport fish and lays a foundation for future research.

Balancing Fisheries Management and Water Uses for Impounded River Systems

<em>Abstract</em>.—In the 1990s, the Minnesota Department of Natural Resources, Fisheries Section, responded to angler requests to manage the state’s waters on a more individual basis. Individual waters management often included the development of length-based regulations and/or bag limit reductions. Although the move towards individual waters management was biologically sound and by and large supported by anglers, it also created some problems. By the late 1990s, there were more than 150 specialized regulations for northern pike <em>Esox lucius</em>, walleyes <em>Sander vitreus</em>, largemouth bass <em>Micropterus salmoides</em>, smallmouth bass <em>M. dolomieu</em>, black crappies <em>Pomoxis nigromaculatus</em>, white crappies <em>P. annularis</em>, and bluegills <em>Lepomis macrochirus</em>. With management responsibility on more than 6,000 lakes, it became clear that some type of regulation streamlining or standardization was needed. Public input meetings indicated that anglers wanted continued individualized management of lakes and the opportunity to catch quality-sized fish but were concerned about the growing number and complexity of regulations. In response, species-specific work groups consisting of research and management biologists were formed to identify what biological information was available and what was needed to develop a set of species-specific regulations. Standardized regulations were developed for northern pike, walleyes, largemouth and smallmouth bass, bluegills, and both species of crappies. We discuss the development of the standardized regulations for crappies, where size and bag limit categories were established based on growth and natural mortality targets. Future field collections will be required to measure the effectiveness of these regulations.

Balancing Fisheries Management and Water Uses for Impounded River Systems

<em>Abstract</em>.—We evaluated the influence of lake morphometry, water quality, and common carp <em>Cyprinus carpio </em>and largemouth bass <em>Micropterus salmoides </em>population structure on quality black crappie <em>Pomoxis nigromaculatus </em>and bluegill <em>Lepomis macrochirus </em>populations for 20 Iowa impoundments. Growth of black crappie was positively related to growth of largemouth bass. Black crappie catch per unit effort (CPUE) was positively associated with watershed size and alkalinity and negatively related to largemouth bass growth. Size structure of bluegill populations was positively influenced by chlorophyll concentrations and largemouth bass catch rates. Total phosphorus and CPUE of stock-to-quality length largemouth bass were also positively related to bluegill growth. Bluegill CPUE was inversely related to largemouth bass growth. Quality largemouth bass populations were allied with turbid (high total suspended solids and low Secchi disk depth) impoundments that had a diverse shoreline and large watersheds. Largemouth bass growth was inversely related to mean depth, and largemouth bass CPUE was inversely related to alkalinity and total suspended solids. Information from this study will be used to classify and rank impoundments in terms of their management priorities. Based on impoundment morphometry and water quality, managers can then target management practices toward species best suited to a particular impoundment.