|Dynamics and growth of the eelpout Zoarces viviparus in the western Dutch Wadden Sea|
Mendez, N. (2014). Dynamics and growth of the eelpout Zoarces viviparus in the western Dutch Wadden Sea. NIOZ-rapport, 2014(2). NIOZ: Texel. 30 pp.
Deel van: NIOZ-rapport. Netherlands Institute for Sea Research (NIOZ): Den Burg. ISSN 0923-3210, meer
In the past the eelpout Zoarces viviparus was considered a resident fish species in the westernDutch Wadden Sea but nowadays it has become rare. In this study, we analysed populationdynamics and growth of Z. viviparus in this area and tried to relate it to changes inenvironmental factors, such as temperature and salinity. In addition, otolith growth patternswere analysed in order to accurately estimate age, an essential requirement to study growth.Long-term trends in abundance showed a drastic population decline since the early 1970s,probably as a consequence of the increment of mean seawater temperature. Springabundance showed significant relationships with temperature and salinity in the previouswinter and summer, while autumn abundance was related to summer temperature andtemperature and salinity in the previous winter. Since growth and reproduction of Z. viviparusseem to be affected by high temperatures, the observed increasing trend in mean annualwater temperature in the western Dutch Wadden Sea suggests that temperatures may beless favourable now than in the past. Otolith analysis showed that the population is mostlycomprised of individuals up to 5 years old. Growth curves fitted with a Von Bertalanffy growthmodel differed between sexes with females having lower L? and higher K than males. Aninterannual comparison of summer growth conditions for 0-group Z. viviparus showed thatyoung eelpout reach a larger size at the end of the growing season in recent years than inthe past. This suggests that despite the low abundances and increasing temperatures, eelpoutgrowth during the first year of life is not negatively affected. A descriptive analysis of eelpoutstomach contents in 2009 showed that its diet is mainly composed of small crustaceans,mostly amphipods and small crabs.