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When ecologically divergent taxa encounter one another, hybrid zones can form when reproductive isolation is incomplete. The location of such hybrid zones can be influenced by environmental variables, and an ecological context can provide unique insights into the mechanisms by which species diverge and are maintained. Two ecologically differentiated species of small benthic fishes, the endemic and imperiled prairie chub, Macrhybopsis australis , and the shoal chub, Macrhybopsis hyostoma , are locally sympatric within the upper Red River Basin of Texas. We integrated population genomic data and environmental data to investigate species divergence and the maintenance of species boundaries in these two species. We found evidence of advanced‐generation asymmetric hybridization and introgression, with shoal chub alleles introgressing more frequently into prairie chubs than the reciprocal. Using a Bayesian Genomic Cline framework, patterns of genomic introgression were revealed to be quite heterogeneous, yet shoal chub alleles were found to have likely selectively introgressed across species boundaries significantly more often than prairie chub alleles, potentially explaining some of the observed asymmetry in hybridization. These patterns were remarkably consistent across two sampled geographic regions of hybridization. Several environmental variables were found to significantly predict individual admixture, suggesting ecological isolation might maintain species boundaries.

This study used microsatellite loci to provide evidence of isolation by distance and an effect of artificial impoundments on the genetic diversity of Channel Catfish Ictalurus punctatus from the Wabash and Ohio rivers. The Wabash River is the longest free‐flowing river east of the Mississippi River in the USA, and the Ohio River is highly impounded, yet both rivers support large Channel Catfish fisheries. There was a significant positive relationship between genetic differentiation and geographic distance indicating isolation by distance. Clustering with the programs, STRUCTURE and GENELAND, and principal component analysis revealed multiple genetic clusters, and several sites had results consistent with adults existing as mixtures of genetic groups. These results suggest that the rate of straying among reproductive sites or dispersal is dependent on geographic distance. Channel Catfish from the unimpounded Wabash River had higher genetic diversity (Ho and He) than that from the impounded Ohio River. The impoundments had discordant effects on genetic structure; two site comparisons across a dam were differentiated more strongly than would be expected by geographic distance, whereas genetic differentiation was not detected in another comparison across a dam. Thus, the effect of artificial impoundments on Channel Catfish biology may be affected by river or site‐specific characteristics, and the presence of genetic differentiation may be minimized by large population sizes.

It has long been recognized that the process of preserving biological specimens results in alterations of body shape, though detailed studies examining the degree to which morphological changes occur throughout the preservation process are lacking. We utilize geometric morphometric analyses, an increasingly common tool for examining shape variation in a wide variety of biological disciplines, to examine the effects of formalin and ethanol preservation on the body shape of 10 freshwater fish species over time: from fresh specimens to eight weeks after preservation. We found significant changes in body shape among fresh and formalin fixed specimens. Furthermore, changes in body shape continue to occur after subsequent ethanol preservation. Two fish species collected at multiple localities show significant morphological differences for a limited number of morphometric characters. However, the significance, or lack thereof, often changed inconsistently from one stage of preservation to another. We conclude that morphometric analyses would ideally be performed on fresh specimens. However, recognizing that this is not always feasible, it is important to be aware of the morphometric changes that can occur during preservation.

Background: Passive integrated transponder (PIT) tags have been used to document and monitor the movement, behavior, or survival of numerous species of fishes. Data on short-and long-term survival and tag retention are needed before initiating studies using PIT tags on a new species or life stage. We evaluated the survival and tag retention of 153 metamorphosing juvenile sea lamprey Petromyzon marinus tagged with 12-mm PIT tags on three occasions using a simple surgical procedure. Results:Tag retention was 100 and 98.6% at 24 h and 28-105 days post-tagging. Of the lamprey that retained their tags, 87.3% had incisions sufficiently healed to prevent further loss. Survival was 100 and 92.7% at 24 h and 41-118 day post-tagging with no significant difference in survival between tagged and untagged control lamprey. Of the 11 lamprey that died, four had symptoms that indicated their death was directly related to tagging. Survival was positively correlated with sea lamprey length. Conclusions:Given the overall high level of survival and tag retention in this study, future studies can utilize 12-mm PIT tags to monitor metamorphosing juvenile sea lamprey movement and migration patterns.

Lake Champlain is consistently ranked as one of the top fisheries for black bass Micropterus spp. in the United States. Tournament fishing on the lake has become increasingly popular, with dozens of tournaments held annually since the early 2000s and at least 60 more planned for 2017. The largest of these tournaments launch from Plattsburgh, New York, and their frequency has generated concerns among fishery managers and the public over post‐weigh‐in mortality and stockpiling. However, relatively little is known about the disposition of tournament‐caught black bass in large (>750 km2) lake systems. To address this information gap, we T‐bar‐tagged 1,141 Largemouth Bass M. salmoides and 1,160 Smallmouth Bass M. dolomieu collected from tournament anglers launching from Plattsburgh during 2011 and 2012. Additionally, 38 Largemouth Bass and 53 Smallmouth Bass caught during professional bass tournaments were implanted with radio tags prior to release. Angler‐reported T‐bar recaptures yielded a 9.8% recovery rate, with over half of the tag recoveries occurring within the first month postrelease, primarily within 5 km of their release. Radio‐tagged fish were tracked for up to 383 d following release into Cumberland Bay, 1 km northeast of Plattsburgh. Overall, 43% of radio‐tagged Largemouth Bass and 56% of radio‐tagged Smallmouth Bass left the bay, although there was variation in dispersal patterns between years. One T‐bar‐tagged fish and no radio‐tagged fish returned to their proximate capture locations. Despite the absence of fish returning to their original capture location, results from both T‐bar tagging and radiotelemetry suggest that long‐term (>1 month) stockpiling in Cumberland Bay is not an issue. However, short‐term (<1 month) stockpiling, coupled with an abundance of publicly accessible fishing areas in Plattsburgh, may warrant concern for increased black bass mortality during the weeks after release. Received April 24, 2016; accepted February 8, 2017 Published online April 4, 2017

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