Effects of seismic sound on spawning behaviour and reproductive sucsess of cod

Anthropogenic noise in the sea are increasing, and the environmental impact of such noise pollution is a growing concern. The SpawnSeis project aimed to resolve how the most widespread noise from petroleum activity, seismic airguns, impacts reproduction of Atlantic cod (Gadus morhua) by looking at spawning habitat usage, egg fertilization rates and hatching success. Cod is one of the most abundant fish species in Norwegian waters, and of the utmost economic, ecological and cultural importance. Cod is also a highly vocal fish, with males producing low frequency grunts to attract female partners. Acoustic signaling by males in spawning shoals also assumably attract females as a long-range signal to locate such shoals. Over two spawning seasons, we have monitored spawning behavior and collected eggs daily from cod in aquaculture netpens before, during and after exposure to seismic air gun shooting. Continuous monitoring by video, hydrophones and echosounder provide detailed data on changes in behavior, vocalization and distribution in response to the exposure. Unfortunately, the exposure period was shorter than planed due to air gun failure. Based on this short exposure, preliminary results indicate neither egg-quality, hatching success nor spawning period are significantly affected by seismic exposure. The cod reacted increased swimming speed and diving to the first air gun shot, but the response was short and mainly towards the very first exposure. Additionally, we have been monitoring movement and habitat use of wild adult cod at a spawning ground in 3D using telemetry tracking technology over three years; one baseline year and two years with seismic exposure during the spawning period. Preliminary results indicate that the cod do not leave their spawning area in response to the seismic, but possibly dive somewhat deeper during exposure. In this project we used a down-scaled air gun, with a sound level comparable to a distance of 10-20 km from a conventional seismic survey. Effects of level higher than those used here can therefore not be ruled out. The project is of high importance to achieve the aim of scientifically based management of seismic explorations in Norwegian waters and minimizing any harmful effects on fishes and ecosystems.

Prosjektet har generert ny, viktig kunnskap om hvordan fisk påvirkes av menneskeskapt støy i gyteperioden, som er svært viktig for å kunne gi kunnskapsbaserte råd til forvaltningen om gjennomføring geofysiske undersøkelser. I dag er rådet å unngå seismikk i gyteområder/perioder med 20 nmi buffersone Resultatene fra dette prosjektet vil bli justert og oppdatert når resultatene har vært gjennom en per review prosess og er publisert. Prosjektet ansatte en postdoktor som i løpet av prosjektperioden har fått fast ansettelse på Havforskningsinstituttet. Prosjektet har hatt to masterstudenter. Prosjektdeltagerne har hatt tett dialog med næringsaktører og dette har blitt brukt til å generere et nytt forskningsprosjekt bygget på kunnskapen fra SpawnSeis. Dette vil undersøke hvordan en ny, kontinuerlig seismikk-kilde påvirker adferd hos fisk i et direkte sammenliknbart forsøksoppsett for å kunne evaluere hvilken kilde som gir minst mulig påvirkning på fisk.

Impact may vary between species and live stages. This project target cod (Gadus morhua), a widely distributed and important species throughout the Atlantic ocean, with hearing range and sound production overlapping with seismic airguns, as well as spawning sites located in the central north sea where the majority of the seismic activity are conducted, thus causing a major management challenge. Important spawning sites in Lofoten also makes it highly relevant in terms of assessing potential oil exploitation. Successful reproduction are essential for stock recruitment, and sound production and hearing are essential during cod spawning, as successful mating relies on vacillation to time release of spawning products. Spawning may hence be impacted in terms of a) hampered vocalization/masking or b) avoidance of spawning site due to exposure. This project will explore both vocal behavior and movement in time and space, as well as investigate the quality of spawning products in exposed and control groups. Exposure will be done with a downscaled air gun. We will work in close collaboration with a large international consortium targeting to asess the population level effects of seismic exposure on cod. This will contribute to exchange ideas, experience and results. Project results are directly applicable into management of fish stocks during seismic surveys, and results obtained will be used to define mitigation to minimizing impact of seismic surveys on fish, but avoiding unnecessary mitigation restrictions, aiming at a better coexistence between the fishery- and oil industry.