In addition to providing animals with a source of directional or ‘compass’ information, Earth’s magnetic field also provides a potential source of positional or ‘map’ information that animals might exploit to assess location. In less than a generation, the idea that animals use Earth’s magnetic field as a kind of map has gone from a contentious hypothesis to a well-established tenet of animal navigation. Diverse animals ranging from lobsters to birds are now known to use magnetic positional information for a variety of purposes, including staying on track along migratory pathways, adjusting food intake at appropriate points in a migration, remaining within a suitable oceanic region, and navigating toward specific goals. Recent findings also indicate that sea turtles, salmon, and at least some birds imprint on the magnetic field of their natal area when young and use this information to facilitate return as adults, a process that may underlie long-distance natal homing (a.k.a. natal philopatry) in many species. Despite recent progress, much remains to be learned about the organization of magnetic maps, how they develop, and how animals use them in navigation.

In coastal waters, anthropogenic activity and its associated sound have been shown to negatively impact aquatic taxa that rely on sound signaling and reception for navigation, prey location, and intraspecific communication. The oyster toadfish Opsanus tau depends on acoustic communication for reproductive success, as males produce ‘boatwhistle’ calls to attract females to their nesting sites. However, it is unknown if in situ vessel sound impacts intraspecific communication in this species. Passive acoustic monitoring using a 4-hydrophone linear array was conducted in Eel Pond, a small harbor in Woods Hole, MA, USA, to monitor the calling behavior of male toadfish. The number of calls pre- and post-exposure to vessel sound was compared. Individual toadfish were localized, and their approximate sound level exposure was predicted using sound mapping. Following exposure to vessel sound, the number of calls significantly decreased compared to the number of calls pre-exposure, with vessel sound overlapping the frequency range of male toadfish boatwhistles. This study provides support that anthropogenic sound can negatively affect intraspecific communication and suggests that in situ vessel sound has the ability to mask boatwhistles and change the calling behavior of male toadfish. Masking could lead to a reduction in intraspecific communication and lower reproductive efficiency within the Eel Pond toadfish population.

For the oyster toadfish, Opsanus tau, vocal communication and sound detection are critical for reproductive success, however, little is known about how they respond to changes in their acoustic environment. Passive acoustic monitoring was conducted in Eel Pond, MA, USA in the summer months (2017–2019) to investigate vocalization patterns of the resident population and the effect of anthropogenic sound. Male toadfish produce mating vocalizations that are characterized by an initial broadband segment (30–50 ms, 100–1000 Hz) and a longer tonal section (200–650 ms, 100–500 Hz). The pulse repetition rate of the tonal section was significantly related to ambient water temperature during hourly and weekly monitoring. Time difference of arrivals were also used to pinpoint the location of toadfish nests and linked to ambient and anthropogenic sound-maps to understand exposure levels for individual fish. Significantly less vocalizations were detected following exposure to vessel sound (100–12 000 Hz, source level 130 dB re 1 μPa), suggesting individuals changed their vocal behavior in response to anthropogenic activity. Both environmental and the presence of vessel sound influence the acoustic behaviour of toadfish, which could lead to a reduction in communication space, mate attraction and detection.

Identifying where fish inhabit is a fundamentally important topic in ecology and acoustic tools can help management to prioritize acoustically sensitive times and areas. In this study, passive acoustic monitoring is presented as a viable tool for monitoring the positions of vocalizing fish species, like the oyster toadfish. Time of arrival differences (TOADs) of sound recordings on a four-hydrophone array were used to pinpoint the location of male oyster toadfish, Opsanus tau, a sedentary fish that produces boatwhistle vocalizations to attract females. Coupling the TOAD method with cross correlation of the different boatwhistles, individual toadfish were mapped during three-hour periods at dawn, midday, dusk, and midnight to examine the relationship between temporal and spatial trends. Seven individual males were identified within 24.2 m of the hydrophone array and up to 18.2 m of the other individuals. The advantages and disadvantages of using the TOAD method to localize individual fish will be discussed. Additionally, preliminary data on how individual toadfish respond to the anthropogenic sound of passing motorized vessels as well as conspecific boatwhistles will be introduced.

Identifying where fish inhabit is a fundamentally important topic in ecology and management allowing acoustically sensitive times and areas to be prioritized. Passive acoustic localization has the benefit of being a non-invasive and non-destructive observational tool, and provides unbiased data on the position and movement of aquatic animals. This study used the time difference of arrivals (TDOA) of sound recordings on a four-hydrophone array to pinpoint the location of male oyster toadfish, Opsanus tau, a cryptic fish that produces boatwhistles to attract females. Coupling the TDOA method with cross correlation of the different boatwhistles, individual toadfish were mapped during dawn (0523-0823), midday (1123-1423), dusk (1723-2023) and night (2323 - 0223) to examine the relationship between temporal and spatial trends. Seven individual males were identified within 0.5-24.2 m of the hydrophone array and 0.0-18.2 m of the other individuals. Uncertainty in passive acoustics localization was investigated using computer simulations as < 2.0 m within a bearing of 033 to 148 degrees of the linear hydrophone array. Passive acoustic monitoring is presented as a viable tool for monitoring the positions of soniferous species, like the oyster toadfish. The method used in this study could be applied to a variety of soniferous fishes, without disturbing them or their environment. Understanding the location of fishes can be linked to temporal and environmental parameters to investigate ecological trends, as well as to vessel activity to discuss how individuals' respond to anthropogenic noise.