Fisheries and bycatch
In the past 50 years, total world fisheries production has increased steadily from 19.3 million tons in 1950 to more than 154 million tons today. Beyond direct effects of fish removal, fishing also leads to incidental capture of non-target species, termed bycatch. Bycatch species can be species of conservation concern (e.g. marine mammals, sea turtles, seabirds) or commercially viable non-target species, e.g. sharks. Fisheries bycatch is one of the primary causes of observed declines of seabirds, marine mammals, sharks and large predatory fishes, collectively termed marine megafauna. For some depleted species, such as Pacific leatherback (Dermochelys coriacea), vaquita (Phocoena sinus), and the Atlantic humpbacked dolphin (Sousa teuszii), fisheries bycatch has been identified as the single largest threat to extant populations. Characterizing and quantifying bycatch and bycatch limits presents a formidable challenge and is the focus of a number of research projects in the Lewison lab.
Ecotoxicology and ecosystem health
Ecotoxicology is the multidisciplinary study of the effects of toxic chemicals on biological organisms, especially at the population, community, and ecosystem levels. The ultimate goal of this field is to predict the effects of pollution so proactive approaches may be taken to prevent or remediate detrimental effects. In ecosystems already impacted by pollution (i.e. San Diego Bay), ecotoxicological studies can inform the best course of action to restore ecosystem services and functions efficiently and effectively. Members of the Lewison Lab collaborate with Dr. Eunha Hoh in the Graduate School of Public Health to address toxicological impacts to vulnerable vertebrates.
Characterizing the spatial and temporal utilization of habitat by organisms is fundamental aspect of conservation ecology. By studying habitat utilization researchers are able to gain insights into resource use and requirements, behavior, inter and intra-speciific interactions, protected area design, and numerous other factors that are necessary to designing effective wildlife management and conservation strategies. Species’ habitat utilization can be studied via direct observations and remote sensing technologies (e.g. satellite telemetry), which can then be combined with data on environmental factors to describe and predict habitat use patterns.
Understanding how fragmented populations are connected is important for effective management and conservation. Connectivity can refer to either the movement of individuals from one habitat to another or the movement of genes through adjacent populations, commonly referred to as gene flow. Since animal movement and gene flow can be difficult to observe, scientists have developed multiple tools to empirically test for connectivity including both telemetry and genetic analyses. Telemetry employs the use of radio, acoustic, and satellite tags to monitor animal presence and movement. Genetics techniques allow researchers to compare the DNA of individuals in different potential populations to test whether there is likely any genetic exchange among them.
Trophic ecology refers to the feeding relationships of an organism within an ecosystem. Determining the trophic dynamics and interactions of organisms generates an overall understanding of an organism’s role in ecosystem function and nutrient flow processes. Many animals exhibit complex life histories and cryptic behavior which make it difficult to study their trophic interactions. Tools such as stable isotope analysis allow us to investigate the trophic ecology of many animals in order to understand their habitat use, role in mediating nutrient flow, trophic status, critical habitat and migratory habits all of which contribute to developing more effective management and conservation efforts.
Dundas, S.J., Levine, A.S., Lewison, R.L., Samhouri, J.F., White, C., Galloway, A.W.E., Hazen, E.L., Spalding,A., Stier, A., Doerr, A.N., Garza, C., Hill, T., Padilla-Gamino, J., White, J.W., 2020. Integrating Oceans into Climate Policy: Any Green New Deal Needs a Splash of Blue. Conservation Letters, in press.
Chen, H.L., Lewison, R.L., An, L., Tsai, Y.H., Stow, D., Shi, L., Yang, S. 2020. Assessing the effects of payments for ecosystem services programs on forest structure and species biodiversity. Biodiversity and Conservation. https://doi.org/10.1007/s10531-020-01953-3
Moleón, M., J. A. Sánchez-Zapata, J. A. Donázar, E. Revilla, B. Martín-López, C. Gutiérrez-Cánovas, W. M. Getz, Z. Morales-Reyes, A. Campos-Arceiz, L. B. Crowder, M. Galetti, M. González-Suárez, F. He, P. Jordano, R. Lewison, R. Naidoo, N. Owen-Smith, N. Selva, J.-C. Svenning, J. L. Tella, C. Zarfl, S. C. Jähnig, M. W. Hayward, S. Faurby, N. García, A. D. Barnosky, and K. Tockner. 2020. Rethinking megafauna. Proceedings of the Royal Society B: Biological Sciences 287:20192643.
Smith, J. G., M. K. Jennings, E. E. Boydston, K. R. Crooks, H. B. Ernest, S. P. D. Riley, L. E. K. Serieys, and R. L. Lewison. 2020. Carnivore population structure across an urbanization gradient : a regional genetic analysis of bobcats in southern California. Landscape Ecology 4.
Trego, M.L., Whitehead, A., Kellar, N.M., Lauf, M., Lewison, R.L. 2019. Tracking transcriptomic responses to endogenous and exogenous variation in cetaceans in the Southern California Bight. Conservation Physiology 7(1): doi:10.1093/conphys/coz018.
Trego, M.L., Hoh, H., Kellar, N.M., Meszaros, S., Robbins, M.N., Dodder, N.G, Whitehead, A., Lewison, R.L. 2019. Comprehensive Screening Links Halogenated Organic Compounds with Testosterone Levels in Male Delphinus delphis from the Southern California Bight. Environmental Science & Technology 52(5):3101-3109.
Lewison, R.L., Johnson, A.F., Gan, J.B., Pelc, R., Westfall, K., Helvey, M. 2019. Accounting for unintended consequences of resource policy: Connecting research that addresses displacement of environmental impacts. Conservation Letters 2019:e12628.
Hughes, B.B., Wasson, K., Tinker, M.T., Williams, S.L., Carswell, L.P., Boyer, K.E., Beck, M.W., Eby, R., Scoles, R., Staedler, M., Espinosa, S., Hessing-Lewis, M., Foster, E.U., Beheshti, K.M., Grimes, T.M., Becker, B.H., Needles, L., Tomoleoni, J.A., Rudebusch, J., Hines, E., Silliman, B.R. 2019. Species recovery and recolonization of past habitats: lessons for science and conservation from sea otters in estuaries. PeerJ 7:p.e8100.
Sadowski, J.S., Gonzalez, J.A., Lonhart, S.I., Jeppesen, R., Grimes, T.M., Grosholz, E.D. 2018. Temperature‐induced range expansion of a subtropical crab along the California coast. Marine Ecology 39(5):p.e12528.
Drake, K.K., Aiello, C.M., Bowen, L., Lewison, R.L., Esque, T.C., Nussear, K.E., Waters, S.C., Hudson, P.J. 2018. Complex immune responses and molecular reactions to pathogens and disease in a desert reptile (Gopherus agassizii). Ecology and Evolution doi:10.1002/ece3.4897.