Bottom water hypoxia suppresses fish chorusing in estuariesa).

Hypoxia in coastal ecosystems is increasing as a result of water quality declines from nutrient pollution. Hypoxia negatively affects fish populations and marine life, limiting their spawning habitats, population size, and growth. In this study, two approaches were used to understand the effect of hypoxia on the chorusing and reproductive behavior of fishes in estuaries.

Development of a Finite-Difference Time Domain (FDTD) Model for Propagation of Transient Sounds in Very Shallow Water.

This finite-difference time domain (FDTD) model for sound propagation in very shallow water uses pressure and velocity grids with both 3-dimensional Cartesian and 2-dimensional cylindrical implementations. Parameters, including water and sediment properties, can vary in each dimension. Steady-state and transient signals from discrete and distributed sources, such as the surface of a vibrating pile, can be used.

Does Vessel Noise Affect Oyster Toadfish Calling Rates?

The question we addressed in this study is whether oyster toadfish respond to vessel disturbances by calling less when vessels with lower frequency spectra are present in a sound recording and afterward. Long-term data recorders were deployed at the Neuse (high vessel-noise site) and Pamlico (low vessel-noise site) Rivers. There were many fewer toadfish detections at the high vessel-noise site than the low-noise station.

Measurement of an individual silver perch Bairdiella chrysoura sound pressure level in a field recording.

Simultaneous audio and video were recorded of a silver perch Bairdiella chrysoura producing its characteristic drumming sound in the field. The background noise contribution to the total sound pressure level is estimated using sounds that occurred between the pulses of the silver perch sound. This background contribution is subtracted from the total sound to give an estimate of the sound pressure level of the individual fish.

Defining and measuring trophic role similarity in food webs using regular equivalence.

We present a graph theoretic model of analysing food web structure called regular equivalence. Regular equivalence is a method for partitioning the species in a food web into "isotrophic classes" that play the same structural roles, even if they are not directly consuming the same prey or if they do not share the same predators. We contrast regular equivalence models, in which two species are members of the same trophic group if they have trophic links to the same set of other trophic groups, with structural equivalence models, in which species are equivalent if they are connected to the exact same other species.