General Research Interests
I strive to understand how early-life feeding (typically on zooplankton), development, and growth of fishes impacts recruitment to adult populations. Compared to the time spent as adults, the larval and early-juvenile life stages of fishes are disproportionately influential to lifetime reproductive success and hence to managing fisheries. In this context, the common thread to my research is testing mechanistic linkages between the early-life success of fishes and fluctuations in their physical and biological environments. I am fortunate to have had the opportunity to apply this conceptual framework in a diversity of ecosystems throughout my professional career. I have performed experiments in small aquaria in the laboratory, manipulated aquaculture ponds, sampled large inland reservoirs and lakes, and studied plankton dynamics in the Gulf of Mexico. I am currently working to establish projects that will help conserve the native fishes of New Mexico.
Invasion ecology of Daphnia lumholtzi in Southwest Arkansas
Climate change is reshuffling species in time and space, generating novel communities and empty ecological niches that may be filled by non-native species. Daphnia lumholtzi are spiny, planktonic crustaceans native to Africa, Asia, and Australia. In Southwest Arkansas, D. lumholtzi were first reported in Millwood Lake and Lake Erling in 1995. During late August and early September 2021, my undergraduate students and I identified D. lumholtzi adults in surface plankton tows collected in Lake Columbia. We are currently conducting field surveys to quantify cyclomorphosis and seasonal densities in Lake Columbia. We are also planning a series of laboratory experiments to test hypotheses underlying their invasion success and regional persistence, including their interactions with predators and responsiveness to long-term climate change stressors (i.e., elevated temperatures and hypoxia).
Establishing a long-term egg and larval fish survey for eastern New Mexico
Native fishes of the southern Great Plains are increasingly imperiled by habitat fragmentation from dam construction and intense regional drying. To monitor fish assemblage responses to environmental change, I recently established a long-term survey of fish eggs and larvae in the Pecos River near Fort Sumner, New Mexico. During 2018–2019, fish eggs and larvae were collected at two sites using 500 μm drift nets equipped with flow meters. Larvae were also collected in deep pools using light traps. In total, over 4,000 fish eggs and 10,000 fish larvae have been collected to date. Most larvae were collected in drift nets, shortly after dusk, during May and June. Identifications of many larvae are challenging, because they are morphologically cryptic, collected at various developmental stages, and/or are damaged from abrasion in the drift nets. Thus, I am also building a reference library to identify early life stages of fishes by coupling high-resolution photographs with molecular identifications using the cytochrome c oxidase I DNA barcode. We also identifying fish eggs collected in drift nets using DNA barcoding. Results of this study will improve our understanding of how environmental change will impact reproductive effort of native and nonnative fishes.
Catfish feeding experiments, Ohio and Arkansas
As an Assistant Professor of Biology at Southern Arkansas University (SAU), I sought to improve catfish production reliability by understanding the effects of commercial feed provision on diets and growth of Channel and hybrid catfish (Channel Catfish ♀ × Blue Catfish ♂) during the transition from yolk-sac to exogenous feeding. Hatchery managers typically maintain all catfish fry on commercial feeds in flow-through tanks for the first two weeks of life, after which they are stocked in fertilized nursery ponds. Commercial feeds are also added to ponds daily after fry stocking. However, results from my graduate research program in Ohio suggested fish only benefit from live natural prey in ponds, despite daily feed additions. The voluntary diet switch of Channel Catfish fry from commercial feed in hatchery tanks to live prey in ponds suggests zooplankton and insects may constitute the preferred diets of first-feeding catfish. Moreover, restricting catfish to an inert commercial feed during first-feeding may delay, enhance, or alter digestive enzyme expression and thereby influence growth and survival. By understanding how commercial feeds affect early-life diets and digestive ontogeny of catfish, I hope to provide hatchery managers specific recommendations to improve production reliability.
Oil spill research, Mississippi
During 2013–2014, I was a post-doctoral researcher at the University of Southern Mississippi, working in Dr. Frank Hernandez’s Fisheries Oceanography and Ecology Laboratory. In this position, I investigated the impacts of the Deepwater Horizon oil spill on growth and body condition of larval fishes collected before, during, and after the oil spill. The primary goal of the project was to distinguish effects of the oil spill on larvae in the water column against natural environmental variation (e.g., weather patterns, river discharge). This research improves our understanding of how oil spills affect recruitment of larval fish into adult populations and hence what managers might expect into the future. A highlight of this project was finding that Red Snapper larvae were in poorer body condition during and after the oil spill, even after accounting for changes in the physical environment.