Painted Goby Larvae under high-CO2 fail to recognize reef sounds

Atmospheric CO2 levels have been increasing at an unprecedented rate due to anthropogenic activity. Consequently, ocean pCO2 is increasing and pH decreasing, affecting marine life, including fish. For many coastal marine fishes, selection of the adult habitat occurs at the end of the pelagic larval phase. Fish larvae use a range of sensory cues, including sound, for locating settlement habitat. This study tested the effect of elevated CO2 on the ability of settlement-stage temperate fish to use auditory cues from adult coastal reef habitats. Wild late larval stages of painted goby (Pomatoschistus pictus) were exposed to control pCO2 (532 μatm, pH 8.06) and high pCO2 (1503 μatm, pH 7.66) conditions, likely to occur in nearshore regions subjected to upwelling events by the end of the century, and tested in an auditory choice chamber for their preference or avoidance to nighttime reef recordings. Fish reared in control pCO2 conditions discriminated reef soundscapes and were attracted by reef recordings. This behaviour changed in fish reared in the high CO2 conditions, with settlement-stage larvae strongly avoiding reef recordings. This study provides evidence that ocean acidification might affect the auditory responses of larval stages of temperate reef fish species, with potentially significant impacts on their survival.Fundação para a Ciência e a Tecnologia (FCT)info:eu-repo/semantics/publishedVersio

Habitat quality affects sound production and likely distance of detection on coral reefs

The interwoven nature of habitats and their acoustic fingerprints (soundscapes) is being increasingly recognized as a key component of animal ecology. Natural soundscapes are crucial for orientation in many different taxa when seeking suitable breeding grounds or settlement habitats. In the marine environment, coral reef noise is an important navigation cue for settling reef fish larvae and is thus a possible driver of reef population dynamics. We explored reef noise across a gradient of reef qualities, tested sound propagation models against field recordings and combined them with fish audiograms to demonstrate the importance of reef quality in determining which reefs larvae are likely to detect. We found that higher-quality reefs were significantly louder and richer in acoustic events (transient content) than degraded reefs, and observed that sound propagated farther with less attenuation than predicted by classic models. We discuss how zones of detection of poor-quality reefs could be reduced by over an order of magnitude compared to healthy reefs. The present study provides new perspectives on the far reaching effects habitat degradation may have on organisms that utilize soundscapes for orientation towards or away from coral reefs, and highlights the value of sound recordings as a cost-effective reef survey and monitoring tool

Data from: Distinguishing social from nonsocial navigation in moving animal groups, American Naturalist 179(5): 621-632. doi:10.1086/665005

Many animals, such as migrating shoals of fish, navigate in groups. Knowing the mechanisms involved in animal navigation is important when it comes to explaining navigation accuracy, dispersal patterns, population and evolutionary dynamics and consequently the design of conservation strategies. When navigating towards a common target, animals could interact socially by sharing available information directly or indirectly, or each individual could navigate by itself and aggregations may not disperse because all animals are moving towards the same target. Here, we present an analysis technique that uses individual movement trajectories to determine the extent to which individuals in navigating groups interact socially, given knowledge of their target. The basic idea of our approach is that the movement direction of individuals arises from a combination of responses to the environment and to other individuals. We estimate the relative importance of these responses, distinguishing between social and non-social interactions. We develop and test our method using simulated groups and demonstrate its applicability to empirical data in a case study on groups of guppies moving towards shelter in a tank. Our approach is generic and can be extended to different scenarios of animal group movement