H.V. Winter

Common Sole Larvae Survive High Levels of Pile-Driving Sound in Controlled Exposure Experiments

In view of the rapid extension of offshore wind farms, there is an urgent need to improve our knowledge on possible adverse effects of underwater sound generated by pile-driving. Mortality and injuries have been observed in fish exposed to loud impulse sounds, but knowledge on the sound levels at which (sub-)lethal effects occur is limited for juvenile and adult fish, and virtually non-existent for fish eggs and larvae. A device was developed in which fish larvae can be exposed to underwater sound. It consists of a rigid-walled cylindrical chamber driven by an electro-dynamical sound projector. Samples of up to 100 larvae can be exposed simultaneously to a homogeneously distributed sound pressure and particle velocity field. Recorded pile-driving sounds could be reproduced accurately in the frequency range between 50 and 1000 Hz, at zero to peak pressure levels up to 210 dB re 1µPa2 (zero to peak pressures up to 32 kPa) and single pulse sound exposure levels up to 186 dB re 1µPa2s. The device was used to examine lethal effects of sound exposure in common sole (Solea solea) larvae. Different developmental stages were exposed to various levels and durations of pile-driving sound. The highest cumulative sound exposure level applied was 206 dB re 1µPa2s, which corresponds to 100 strikes at a distance of 100 m from a typical North Sea pile-driving site. The results showed no statistically significant differences in mortality between exposure and control groups at sound exposure levels which were well above the US interim criteria for non-auditory tissue damage in fish. Although our findings cannot be extrapolated to fish larvae in general, as interspecific differences in vulnerability to sound exposure may occur, they do indicate that previous assumptions and criteria may need to be revised.

Impulsive sounds change European seabass swimming patterns: Influence of pulse repetition interval

Seismic shootings and offshore pile-driving are regularly performed, emitting significant amounts of noise that may negatively affect fish behaviour. The pulse repetition interval (PRI) of these impulsive sounds may vary considerably and influence the behavioural impact and recovery. Here, we tested the effect of four PRIs (0.5-4.0s) on European seabass swimming patterns in an outdoor basin. At the onset of the sound exposures, the fish swam faster and dived deeper in tighter shoals. PRI affected the immediate and delayed behavioural changes but not the recovery time. Our study highlights that (1) the behavioural changes of captive European seabass were consistent with previous indoor and outdoor studies; (2) PRI could influence behavioural impact differentially, which may have management implications; (3) some acoustic metrics, e.g. SELcum, may have limited predictive power to assess the strength of behavioural impacts of noise. Noise impact assessments need to consider the contribution of sound temporal structure.

Connectivity between migrating and landlocked populations of a diadromous fish species investigated using otolith microchemistry.

Smelt Osmerus eperlanus has two different life history strategies in the Netherlands. The migrating population inhabits the Wadden Sea and spawns in freshwater areas. After the closure of the Afsluitdijk in 1932, part of the smelt population became landlocked. The fresh water smelt population has been in severe decline since 1990, and has strongly negatively impacted the numbers of piscivorous water birds relying on smelt as their main prey. The lakes that were formed after the dike closure, IJsselmeer and Markermeer have been assigned as Natura 2000 sites, based on their importance for (among others) piscivorous water birds. Because of the declining fresh water smelt population, the question arose whether this population is still supported by the diadromous population. Opportunities for exchange between fresh water and the sea are however limited to discharge sluices. The relationship between the diadromous and landlocked smelt population was analysed by means of otolith microchemistry. Our interpretation of otolith strontium (88Sr) patterns from smelt specimens collected in the fresh water area of Lake IJsselmeer and Markermeer, compared to those collected in the nearby marine environment, is that there is currently no evidence for a substantial contribution from the diadromous population to the spawning stock of the landlocked population.

Seasonal migration of the starry smooth-hound shark Mustelus asterias as revealed from tag-recapture data of an angler-led tagging programme.

The primary aim of this long-term angler-led tagging programme was to gain information about seasonal changes in distribution of the starry smooth-hound shark Mustelus asterias, along the Dutch coast for management and conservation purposes. Between 2011 and 2014, M. asterias comprised 92·6% (n = 2418) of the total elasmobranch catch (n = 2612) by the licenced group of taggers within the Dutch Delta of which 2244 M. asterias were fin-tagged with plastic rototags. Sex and total length (LT ) composition inside the eastern tidal basin (Oosterschelde) were significantly different, i.e. more females and larger individuals, than outside indicating a pupping ground, which was confirmed by the capture of 30 newborn pups (≤32 cm). The distribution pattern of reported recaptured M. asterias (return-rate 3·6%, n = 80) showed a circannual migration between summering in the southern North Sea and wintering in the English Channel and the Bay of Biscay, and suggests that M. asterias is philopatric. The Dutch angling season for M. asterias runs from approximately mid-May to mid-October when the water temperature is above 13° C. Recaptures of eight mature females, but no males in the Bay of Biscay, indicate partial spatial segregation by sex, where mature females migrate over larger distances than immature females and males. These observations, with the absence of recaptures in other known summering areas (i.e. the Irish Sea and Bristol Channel), suggest that the southern North Sea is used by a separate population. Implications for management and recommendations to improve and expand the study approach are discussed.

Effect of Pile-Driving Sounds on the Survival of Larval Fish

Concern exists about the potential effects of pile-driving sounds on fish, but evidence is limited, especially for fish larvae. A device was developed to expose larvae to accurately reproduced pile-driving sounds. Controlled exposure experiments were carried out to examine the lethal effects in common sole larvae. No significant effects were observed at zero-to-peak pressure levels up to 210 dB re 1 μPa(2) and cumulative sound exposure levels up to 206 dB re 1 μPa(2)·s, which is well above the US interim criteria for nonauditory tissue damage in fish. Experiments are presently being carried out for European sea bass and herring larvae.

Noise impact on European sea bass behavior : Temporal structure matters

Anthropogenic sounds come in different forms, varying not only in amplitude and frequency spectrum but also in temporal structure. Although fish are sensitive to the temporal characteristics of sound, little is known about how their behavior is affected by anthropogenic sounds of different temporal patterns. We investigated this question using groups of Dicentrarchus labrax (European sea bass) in an outdoor basin. Our data revealed that the temporal pattern of sound exposure is important in noise impact assessments.

Toestand vis en visserij in de zoete Rijkswateren 2016: Deel I: trends

Het rapport “Toestand Vis en Visserij in de Zoete Rijkswateren” bestaat uit drie verschillende delen: Deel I “Trends”, Deel II “Methoden” en Deel III “Data”. In dit rapport (Deel I) worden (i) de trends in commercieel benutte vissoorten per VBC gebied, (ii) de trends in niet-inheemse vissoorten (exoten) en (iii) de trends in ecologische kwaliteitsratio’s vis gerapporteerd. Hiervoor is gebruik gemaakt van de gegevens die binnen de verschillende vismonitoringsprogramma’s op de Zoete Rijkswateren worden verzameld, aangevuld met gegevens over bv. aanlandingen. In de rapportage zijn trendanalyses voor de verschillende commercieel benutte vissoorten en niet-inheemse vissoorten (exoten) gemaakt aan de hand van de beschikbare monitoringsgegevens. De gegevens van deze monitoringsprogramma’s worden gebruikt als indicatoren voor de ontwikkeling van de bestanden van de geanalyseerde soorten over verschillende tijdsperioden. Het rapport concentreert zich op het weergeven van data en trends.

Aalonderzoeken Hoogheemraadschap van Delfland: efficiëntie van glasaalintrek bij gemaal Schoute

Deze studie betreft een analyse van het aanbod en de intrekefficientie van glasaal bij een van de prioritaire intrekpunten van Delfland: gemaal Schoute in Den Haag (Scheveningen). Het complex bij gemaal Schoute bestaat uit een jachthaven, een keersluis (barriere 1), een tussenpand en een gemaal (barriere 2). Deze rapportage beschrijft de nulsituatie van de intrek van glasaal bij gemaal Schoute en gaat in op de onderzoeksvraag: Wat is de intrek-efficientie voor glasaal van het migratie knooppunt te Scheveningen (Keersluis, tussenpand en gemaal Schoute)? Daarnaast wordt middels merken en terugvangst onderzoek van glasaal een (lokale) populatieschatting gemaakt.