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Hawkins A.D.,Loughine Ltd | Pembroke A.E.,Normandeau Associates | Popper A.N.,University of Maryland University College
Reviews in Fish Biology and Fisheries | Year: 2014

The expansion of shipping and aquatic industrial activities in recent years has led to growing concern about the effects of man-made sounds on aquatic life. Sources include (but are not limited to) pleasure boating, fishing, the shipping of goods, offshore exploration for oil and gas, dredging, construction of bridges, harbors, oil and gas platforms, wind farms and other renewable energy devices, and the use of sonar by commercial and military vessels. There are very substantial gaps in our understanding of the effects of these sounds, especially for fishes and invertebrates. Currently, it is almost impossible to come to clear conclusions on the nature and levels of man-made sound that have potential to cause effects upon these animals. In order to develop a better understanding of effects of man-made sound, this paper identifies the most critical information needs and data gaps on the effects of various sounds on fishes, fisheries, and invertebrates resulting from the use of sound-generating devices. It highlights the major issues and discusses the information currently available on each of the information needs and data gaps. The paper then identifies the critical questions concerning the effects of man-made sounds on aquatic life for which answers are not readily available and articulates the types of information needed to fulfill each of these drivers for information—the key information gaps. Finally, a list of priorities for research and development is presented. © 2014, Springer International Publishing Switzerland.

Hawkins A.,Loughine Ltd | Knudsen F.R.,Fisheries Research | Davenport J.,University College Cork | McAllen R.,University College Cork | And 4 more authors.
Journal of Experimental Marine Biology and Ecology | Year: 2012

We have investigated grazing by sprat schools upon zooplankton within Lough Hyne (Ireland), a marine lake with only a narrow and shallow connection to the sea. Acoustic surveys showed the presence of large numbers of sprat (Sprattus sprattus), preyed upon by mackerel Scomber scombrus. The sprat formed dense schools during the day and dispersed at night. Zooplankton were widely distributed within the lough, although absent below the oxythermocline. However, echo traces showed clear volumes, indicating an absence of zooplankton, surrounding the daytime sprat schools. Pumped sampling of the zooplankton at different depths, close to and away from the sprat schools, confirmed that those volumes of water that appeared acoustically clear were largely devoid of macro zooplankton (92.7% reduction overall). Comparison of clear areas with adjacent areas showed that almost all decapod larvae and calanoid copepods and most bivalve larvae were absent. The differences for cladocerans were also significant but for gastropod larvae they were not significant. Large calanoid copepods were much less abundant in the clear areas and their size distribution had changed. We conclude that the sprat schools had rapidly depleted their surroundings of zooplankton, suggesting that fish within the schools may be substantially food-limited. Dispersal at night, when visual predators are less efficient, may enable the sprat to feed more effectively. Thus, although schooling may confer benefits to individual fish there are concomitant disadvantages in terms of food depletion. The reduction in zooplankton as a result of heavy grazing by sprat within the enclosed lough may affect the phytoplankton, with significant effects upon the ecology of Lough Hyne. © 2011 Elsevier B.V.

McWilliam J.N.,Northumbria University | Hawkins A.D.,Loughine Ltd
Journal of Experimental Marine Biology and Ecology | Year: 2013

Sound travels well through water and is capable of conveying information to any listener on both the presence of particular organisms and the quality of the environment. Many marine organisms use sounds to navigate, forage and communicate, while different marine habitats often have their own acoustical characteristics. However, there are still large gaps in our knowledge of marine soundscapes, particularly in regard to their spatial patterns. The goal of this research was to investigate passive acoustic monitoring as an ecological survey technique. The specific objectives were to compare soundscapes between and within benthic habitats and to evaluate the influence of different environmental factors. Acoustic recordings were made in Lough Hyne, Ireland during May 2012, following a nested design in three benthic habitats; Mud, Gravel and Cliff. Three patches of each habitat were selected using hydro-acoustic and underwater video surveys and within each patch five different sites were monitored (n. = 45). A nested analysis of variance (ANOVA) showed that acoustic profiles differed significantly within but not between habitats, although unique acoustic signatures existed over different spatial ranges, illustrating a degree of stability at local patch level. A distinct peak (2-4. kHz) in acoustic complexity was observed in all habitat patches but one, and was caused by the presence of transient broadband pulses or snaps. These snaps were attributed to the presence of snapping shrimp (family Alpheidae), found at a particular location within the lough. Other distinctive sounds of suspected biological origin were identified in particular habitat patches (Cliff and Gravel) and suggested the presence of habitat related biophonies. Soundscape signatures of different patches were strongly correlated with proximity to the source of the high-energy snaps, indicating that location was more important than habitat in determining soundscape characteristics. Other environmental factors such as bottom type and depth were less important. It is evident that acoustical sources of high energy and broadband properties have pervasive effects over considerable distances (up to 1. km). The acoustic characteristics of a habitat patch were greatly influenced by extraneous sounds, in this case from a biological source. The high acoustic connectedness of marine habitats underlines the need for evaluating the impact of anthropogenic activities, particularly for ecosystems with unique biophonies in need of protection. There is potential for developing passive acoustic monitoring as a principal method for surveying marine habitats and observing local processes at different spatial and temporal scales. © 2013 Elsevier B.V.

Cott P.A.,Northwest Atlantic Fisheries Center | Cott P.A.,Laurentian University | Hawkins A.D.,Loughine Ltd | Zeddies D.,JASCO Applied science | And 6 more authors.
Journal of Great Lakes Research | Year: 2014

Burbot (Lota lota) are northern freshwater gadoid fish that spawn under ice-cover, making their reproductive behavior largely unknown to science. Some members of the cod family vocalize as part of their mating system. These calls are produced by rapidly contracting drumming muscles on their swim bladders. Burbot also possess drumming muscles, like their marine counterparts, which may enable them to vocalize. To assess the potential for burbot to make calls, pre-spawning adult burbot were collected and placed in a large under-ice enclosure in Great Slave Lake, Northwest Territories, Canada, along with a recorder that monitored low frequency sound over their spawning period. The recorded acoustic data revealed that burbot called coincident with the onset of their spawning period and that the call signatures were stereotypical of swim bladder generated vocalizations made by other gadoid fishes. Burbot showed a wide repertoire of calls, from slow knocks to fast buzzing, similar to the closely related haddock (Melanogrammus aeglefinus). Although never-before documented, calling by fish under ice-cover is likely an important part of the mating system of under-ice spawning gadoids because light limitation would reduce the usefulness of visual cues. These under-ice communications may be affected by anthropogenic noise from increasing resource development in northern regions. © 2014 Elsevier B.V.

Krysl P.,University of California at San Diego | Hawkins A.D.,Loughine Ltd | Schilt C.,Bigleaf Science Services | Cranford T.W.,Quantitative Morphology Consulting Inc.
PLoS ONE | Year: 2012

Fish can sense a wide variety of sounds by means of the otolith organs of the inner ear. Among the incompletely understood components of this process are the patterns of movement of the otoliths vis-à-vis fish head or whole-body movement. How complex are the motions? How does the otolith organ respond to sounds from different directions and frequencies? In the present work we examine the responses of a dense rigid scatterer (representing the otolith) suspended in an acoustic fluid to low-frequency planar progressive acoustic waves. A simple mechanical model, which predicts both translational and angular oscillation, is formulated. The responses of simple shapes (sphere and hemisphere) are analyzed with an acoustic finite element model. The hemispherical scatterer is found to oscillate both in the direction of the propagation of the progressive waves and also in the plane of the wavefront as a result of angular motion. The models predict that this characteristic will be shared by other irregularly-shaped scatterers, including fish otoliths, which could provide the fish hearing mechanisms with an additional component of oscillation and therefore one more source of acoustical cues. © 2012 Krysl et al.

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