Abstract
There are growing needs to understand biological effects on fishes and aquatic invertebrates resulting from exposure to underwater particle motion and substrate-borne vibration associated with offshore energy activities. These activities include, but may not be limited to, offshore renewable energy development regulated by the Bureau of Ocean Energy Management (BOEM). However, studies to investigate such effects face multiple challenges due to the complexity of the acoustic field, which involves water-borne particle motion and substrate-borne vibration. Without appropriate experimental designs and studies, it would be difficult or even impossible to understand the biological and physiological effects on fishes and aquatic invertebrates.
Over the past several years, the scientific community has become increasingly aware that most fishes and aquatic invertebrates sense acoustic energy in the form of particle motion and substrate-borne vibration, and that significant data gaps exist concerning potential biological effects on animals of these disturbances from offshore energy development (e.g., Hawkins et al., 2021; Popper and Hawkins, 2018). However, studies to address these interdisciplinary issues often face challenges regarding the appropriate experimental setting, measurement collection, and data interpretation. In a laboratory environment, careful consideration must be given regarding boundary conditions, sediment types and thickness, and measurements of animals’ behavioral, audiometric, and physiological response (Hawkins et al., 2021, p. 2; Roberts et al., 2016b).
To address these issues, BOEM convened a virtual Workshop on Research Methodologies to Study Biological Effects from Particle Motion and Substrate-Borne Vibration on 19–20 October 2023. The Workshop brought together researchers and experts in the areas of (1) fish and aquatic invertebrate sensory biology and biotremology (the study of biological use of vibrations), and (2) physical and engineering acoustics. The goal was to provide recommendations on general experimental design, sound and substrate-borne vibration apparatuses, and testing procedures that are appropriate to address specific research questions. These questions include whether fishes and aquatic invertebrates can be grouped under different functional hearing groups based on their auditory mechanisms or hearing sensitivity and whether exposure to anthropogenic particle motion or substrate-borne vibration would cause changes in vital rates or hormone levels in fishes and aquatic invertebrates. In addition, representatives from major funding agencies and regulators also participated the Workshop to gain knowledge of this field. The workshop included five keynote talks and breakout group discussions. The keynote talks focused on reviews of research designs and fundamental physical acoustic concepts related to study behavioral and physiological effects from underwater particle motion and substrate-borne vibration on fishes and aquatic invertebrates. These keynote talks were the following:
• Arthur N. Popper: “Sound Pressure, Particle Motion, Substrate Vibration – A History of Rethinking Fish (and Invertebrate) Hearing”
• James Martin: “A Review of Vibroacoustic Wave Generation Devices that Are Suitable to Fishes and Invertebrates Acoustic Studies in Laboratory Settings”
• Joseph A. Sisneros: “A Review of Proper Experimental Design and Lessons Learned from Fish Vibroacoustic Research Under Laboratory Settings”
• James H. Miller: “A Review of Physical Characteristics of Particle Motion, Substrate-Borne Vibration, and Interface Waves that Are Biologically Relevant”
• Louise Roberts: “A Review of Proper Experimental Design and Lessons Learned from Invertebrates Vibroacoustic Research Under Laboratory Settings”
Breakout group sessions served as platforms for experts to discuss and respond to a set of questions directed at identifying appropriate research methodologies to study behavioral and physiological effects from underwater particle motion and substrate-borne vibration exposure on fishes and aquatic invertebrates.
A very important outcome of the breakout groups was the idea that one must first determine the research questions and then select the most appropriate experimental approach to answer those questions. Thus, the research question(s) must drive how they are answered.
A second critical outcome of the discussions was how research questions—and research approaches—are likely to differ depending on the species of interest, as well as on the age and size of the animals studied. Thus, an experimental approach that may be appropriate for larval fishes may not be suitable for adults, and an experimental approach that works for a sessile species may not be suitable for a mobile species. The participants also recognized that the outcome of the current workshop was building upon several earlier workshops conducted by BOEM and other agencies. Based on these prior workshops and associated studies, this report identifies 20 major research questions. These research questions are grouped into four major series: auditory mechanism; hearing effects; behavioral effects; and physiological effects.
To link specific research questions with appropriate experimental designs, the report identifies four basic experimental settings: (1) laboratory tank; (2) in-ground pond/tank or above-ground tank; (3) large water body, such as a pond, river, lake, or ocean/bay with animals confined in cages (open-water, confined); and (4) large water body with free-ranging animals (open-water, free-ranging).
Finally, the report provides initial views of pros and cons of these four different experimental settings to study fishes and aquatic invertebrates and the behavioral and physiological effects from particle motion and substrate-borne vibration exposure. The report then suggests research questions that can and cannot be addressed under each of the experimental settings (Tables 1 and 2 in the main document).