Rev Fish Biol Fisheries (2015) 25:425–447 DOI 10.1007/s11160-015-9393-y REVIEWS Physiology in the service of fisheries science: Why thinking mechanistically matters Andrij Z. Horodysky . Steven J. Cooke . Richard W. Brill Received: 7 January 2015 / Accepted: 13 July 2015 / Published online: 21 July 2015 Ó Springer International Publishing Switzerland 2015 Abstract Behavioral responses of fishes to variabil- stock size occurring over time. Because physiology is ity in environmental conditions and habitat quality are the transfer function that links specific environmental central to population-level demographic processes. conditions to behavior and fitness, we argue great gains Although field surveys can correlate abundance to can be made through the integration of physiology and habitat variables (physiochemical, biotic, and struc- fisheries science. These are complementary disci- tural), they cannot provide mechanistic explanations. plines, albeit ones that generally function at very Moreover, field surveys are often stratified by time or different temporal and spatial scales, as well as geographic criteria relevant to humans, whereas fishes different levels of biological organization. We argue stratify by habitat variables relevant to them. If more specifically that integrating physiological mechanisms underlying behavior are not explicitly approaches with behavioral studies and traditional understood, conclusions based on survey data can lead fisheries survey data (where each approach develops to biased inferences as to species-specific habitat hypotheses to be tested in the other) can mechanisti- requirements and preferences, as well as changes in cally link processes from cells through populations to place fisheries management in an appropriate ecosys- tem context. We further contend that population- and A. Z. Horodysky (&) species-specific mechanistic understanding of physio- Department of Marine and Environmental Science, logical abilities and tolerances can significantly help Hampton University, 100 E. Queen St, Hampton, VA 23668, USA to: improve stock assessments, describe essential fish e-mail: [email protected] habitat, predict rates of post-release mortality, develop effective bycatch reduction strategies, and forecast the S. J. Cooke population effects of increases in global temperatures Fish Ecology and Conservation Physiology Laboratory, Department of Biology and Institute of Environmental and ocean acidification. Science, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1S 5B6, Canada Keywords Aquaculture Á Bycatch Á Climate change Á Ecology Á Fisheries Á Fry’s paradigm Á Physiology Á R. W. Brill National Marine Fisheries Service, Northeast Fisheries Post-release survival Science Center, 166 Water Street, Woods Hole, MA 02543, USA Introduction R. W. Brill Virginia Institute of Marine Science, College of William Natural and anthropogenic changes to the structure & Mary, Gloucester Point, VA 23062, USA and function of global ecosystems paint a future of 123 426 Rev Fish Biol Fisheries (2015) 25:425–447 potentially unstable food security for humans (Roseg- scales of days to centuries; and over spatial scales from rant and Cline 2003). Global fisheries are simultane- a habitat patch to ocean basins with a focus on ously fishing down and farming up food webs to meet populations, communities, and ecosystems. Fisheries the ever-increasing demands for protein of a burgeon- science provides inferences that range from descrip- ing world population (Pauly et al. 1998; Naylor et al. tive to highly quantitative, but that are rarely mech- 2000; Jackson et al. 2001; Essington et al. 2006; Worm anistic in isolation (Smith 2002). We contend that et al. 2009). Humans are thus demanding more synoptic understanding of the environment-organism- productivity from aquatic habitats at a time when ecosystem interface will be greatly advanced through directional climate change and ocean acidification interdisciplinary collaborations between the mecha- further threaten the health of aquatic ecosystems nistically-driven physiological sciences, the pattern- worldwide (Sumaila et al. 2011; Halpern et al. 2012). oriented behavioral sciences, and the quantitatively- A sustainable future necessitates understanding the driven fisheries sciences. relationship of fisheries resources to environmental The disciplines of physiology and ecology, whether variation, including perturbations of anthropogenic through training, funding, or charge, differentially origin. approach the fundamental versus applied science In this synthesis, we therefore cover advances continuum. Physiologists have historically investi- arising from a synergistic view of fish physiology and gated questions that piqued their intellectual curiosity, field fisheries ecology, first in the context of ecological often using a reductionist approach to minimize sciences, and second, in the context of applied variation (Mangum and Hochachka 1998). Fishery fisheries science. Fish physiology and fisheries science biologists, in contrast, have traditionally conducted are complementary disciplines that function at differ- multivariable research more concerned with optimal ent temporal and spatial scales, but are united at the or sustainable harvesting strategies (Ulltang 1998; study of individual behavior (Fig. 1). Fish physiolo- Rothschild and Beamish 2009), or (more recently) gists typically investigate questions over temporal with mitigating the profound effects that humans have scales from milliseconds to seasons, and over spatial on the living aquatic world (Halpern et al. 2008) and scales from the sub-micron to mesocosms, with a educating society about the need for resource conser- primary focus on cellular, organ, and organismal vation (e.g., Jacquet and Pauly 2007). It is long function. Such investigations typically try to identify overdue for this dichotomy to be jettisoned because cause and effect relationships, providing mechanistic fertile interdisciplinary ground exists, especially when insights at the level of the individual or below, but fisheries scientists consider directly the mechanistic they may not scale to meaningful population and basis underlying the hypotheses and field-observed ecosystem contexts in isolation. By contrast, fisheries patterns they are investigating, and when physiologists scientists (including ecologists and population biolo- reach beyond reductionist approaches and univariate gists) typically investigate questions over temporal statistical analyses so that inferences can scale Fig. 1 Complementary Biosphere Ecosystem temporal, spatial, and Ocean Basin Community Descriptive or organizational scales of fish Species Range Fisheries Species Organizational Scale physiology and fisheries quantitative, biology. The intersection Seascape but rarely mechanistic Biology Population between these disciplines— Habitat patch Subpopulation the study of behavior and Whole organism Behavior, Fitness Individual (internal fitness (including growth, milieu Organ survival, and Spatial Scale or Tissue reproduction)—is fertile in vivo) Fish Physiology ground for collaboration Primarily Cell mechanistic, rarely quantitative Organelle In vitro Molecule Millisecond Second Minute Hour Day Month Year Decade Century Temporal Scale 123 Rev Fish Biol Fisheries (2015) 25:425–447 427 meaningfully to the population level. This incorpora- collaboration (e.g., Iwama et al. 1997), we focus this tion, however, generally requires a detailed under- synthesis on the interactions between physiology and standing of physiological principles that fisheries the field-based and quantitative ecological sciences. biologists—and of quantitative techniques and applied fisheries-relevant issues that fish physiologists—are generally ill-equipped to apply (by interest, training, The need for understanding how fishes relate and available resources) or many not fully appreciate. to the environment The direct interaction of the physiological and fisheries sciences, and collaboration with the ecosys- Defining how animals relate to their environment bears tem sciences, economics, and the social sciences, consequences for how the disciplines of physiology holds the potential to describe and forecast the effects and ecology approach studying them, with clear of natural and anthropogenic changes on fisheries, and implications for management and policy. Following to address the societal concerns that operate at the the seminal work of Frederick Fry, fish physiologists scale of populations, communities, and ecosystems have generally used an autecological approach to (Metcalfe et al. 2012). Similar arguments are also define how environmental resources and habitat affect being made for the integration of physiology, behav- an individual; whereas following the seminal work of ior, and ecology, especially as it relates to predicting G. Evelyn Hutchenson, fisheries ecologists and mod- the effects of anthropogenic activities (e.g., climate elers generally follow a synecological focus on how change, deforestation, pollution) on the world’s interacting individuals and species affect the environ- ecosystems and preservation of critical ecosystem ment (Devictor et al. 2010). Fry (1947) elucidated the services (e.g., Chown and Gaston 2008; Denny and metabolic basis for behavior and activity in response to Helmuth 2009; Helmuth 2010; Sih et al. 2010). environmental conditions, defining the metabolic In this synthesis, we briefly describe the potential scope for activity (the difference between maximum for productive interdisciplinary collaboration