Analysis of the contribution of the Netherlands commercial CPUE data to ICES stock assessments in the years 1995 - 2000

The contribution of the Dutch commercial CPUE data to the stock assessments of North Sea plaice and sole in the years 1995-2000 has been analysed. The CPUE series are based on the total landings at age in the Dutch beam trawl fishery and the total effort (in HP days at sea) of this fishery. It is shown that the contribution of the sole CPUE data to the final XSA assessments is higher that the contribution of the plaice CPUE data. It is discussed what the general role is of commercial CPUE data in the calibration process of a stock assessment model. The reason for the higher contribution of the sole CPUE data is explained. It is further discussed what the potential caveats are for the use of commercial CPUE data and how that applies to e.g. North Sea plaice

Trends in Wadden Sea Fish Fauna, Part II: Dutch Demersal Fish Survey (DFS)

Shallow waters along the North Sea coast provide nursery areas for juveniles of several fish species, including commercially exploited species, and natural habitat for resident species and seasonal visitors. These areas have gone through major changes in the last decades due to climate change and human activities, which will likely result in changes in the abundance and species composition of the fish fauna in coastal waters

Follow-up on initiatives taken by the TMAP ad hoc working group fish in 2006

Since 1978, The Netherlands, Denmark and Germany have been working together on the protection and conservation of the Wadden Sea covering management, monitoring and research, and political matters. An important element of the Trilateral Cooperation with regards to monitoring and research is the Quality Status Report (QSR). This report is published every 5 years and it presents the results various ongoing monitoring programs in the Wadden Sea. Another important element of the Trilateral Cooperation is the Trilateral Monitoring and Assessment Program (TMAP) which aims at providing a scientific assessment of the status and changes in the ecosystem, and the effectiveness of implementing targets set by Trilateral Wadden Sea Plan. The results of these monitoring and assessment programs are presented in the QSR. Finally, the Trilateral Cooperation with regards to monitoring and research is facilitated and enhanced by means of the International Scientific Wadden Sea Symposia

Passende Beoordeling windparken: Effecten van heien op vislarven, vogels en zeezoogdieren

Dit rapport vormt een aparte bijlage bij de Passende Beoordeling (PB) Windparken van Royal Haskoning (Boon & Arends 2009), waarin effecten van de bouw van een twintigtal offshore windparken op de kwaliteit van zoute Natura 2000-gebieden worden beschreven. In dit deelonderzoek is het effect van het heien op de kinderkamerfunctie en het voedselaanbod voor vogels en zeezoogdieren in Natura 2000-gebieden bestudeer

Demersal Fish Survey gegevens van het Eierlandsche Gat

In het kader van een MER voor het leggen van een kabel tussen Texel en Vlieland, is het RIVO gevraagd om gegevens te leveren van de visfauna in het Eierlandsche Gat. Dit gebied wordt tijdens de “Demersal Fish Survey (DFS)” bemonsterd

Review of the spatial and temporal distribution by life stage for 19 North Sea fish species

Considering the increase in human activity in the North Sea, particularly cargo shipping and the rapidly expanding construction and operation of oil platforms and wind farms, as well as the continued use of the area for military purposes, fisheries and sand extraction, there is a growing concern about the potentially harmful impacts of such anthropogenic activities on marine life. Particular concerns have been raised about the effect of loud impulse sounds and high noise levels, which may affect marine animal life in different ways: habitat use, such as feeding and migration, and reproduction patterns may be disturbed. In the extreme case animals may suffer from sub-lethal or lethal physical damage such as hearing loss and disrupted swim ladders. Knowledge of the spatial distribution and seasonal patterns in the presence of different life stages of marine species is therefore critical for assessing to what extent the dispersion of marine life overlaps with the distribution of human activities and for estimating how potentially harmful impacts can be mitigated both spatially and temporally. The aim of this desk study is consequently to provide a concise overview of existing information on seasonal patterns in the dispersion of fish species in the North Sea, in particular by highlighting the knowledge gaps

Species identification workshops 2012 and 2013: Gobies and Elasmobranchs

Up until now, gobies of the genus Pomatoschistus have not been identified to the lowest taxonomic level during The Demersal Fish Survey (DFS), Sole Net Survey (SNS) and Beam Trawl Survey (BTS). It is however an abundant genus in the catches in the shallow coastal zone stations and it can be assumed that the species play a role in the coastal ecosystem. The correct identification on board is however questionable. For that reason, during the 2012 DFS extra attention has been paid to identification of Pomatoschistus species. On each of the three vessels carrying out the DFS, a Pomatoschistus expert (Cindy van Damme or Bram Couperus) was taken on board for one week. On board Stern and Schollevaar all Pomatoschistus have been identified to the species, and on board Isis part of the specimens were identified to the species, and part was taken to the lab. Samples were frozen following a protocol to keep the quality of the fish as good as possible and were taken back to the lab for identification. Main problems arose in identification of P. lozanoi and P. minutus. As even the experts did not agree, it is proposed to treat P. lozanoi and P. minutus as a group of species, and to identify the other species to the species level. From identification workshops and tests on demersal fish and benthos it became clear that specific attention should be paid to the elasmobranch species. On 20 March 2013 a dedicated species identification workshop focusing on elasmobranch species was organised for IMARES employees. Main purpose of the workshop was quality assurance of species identification of elasmobranch species. IMARES projects influenced by the quality of this species identification are i.a. the seagoing statutory task surveys, statutory task discard projects, PULSMON. The species to be identified were collected during the BTS2011 and BTS 2012 and stored in the freezer. Results are presented by expertise level of the employees. The expertise level was based on expertise and responsibilities during surveys and discard sampling. The results of the test and workshop were in line with earlier workshops focusing on fish and macrobenthos

Developments in benthos and fish in gullies in an area closed for human use in the Wadden Sea : 2002-2016

In the eastern Dutch Wadden Sea an area was closed for anthropogenic bottom-disturbing activities in 2005. The ‘natural’ development of the fauna in gullies located within this area was monitored and compared with the development in gullies outside the closed area. Emphasis was put on sampling the benthic fauna (every autumn). Eleven years after closure (2016) the fish population was sampled again and additional benthic samples were taken, the sea floor was mapped and the fishing pressures were calculated. Preliminary results show that throughout the investigated period the open gullies were subject to moderate shrimp fishing pressures and that the closed gullies were not fished. Closure of the gullies has not yet led to the formation of biogenic structures on the seafloor, but has led to an increase in the species richness of small benthic fauna and to subtle changes in benthic species composition. Due to the limited availability of data it was not possible to detect statistically significant differences in the fish population. Sinds november 2005 is een klein deel van de Nederlandse Waddenzee gesloten voor (potentieel) schadelijke menselijke activiteiten. Het gebied ligt ten zuiden van Rottumerplaat en Rottumeroog en beslaat zo’n 7400 hectare. Doel van de sluiting is om de ongestoorde ontwikkeling van de natuur in de Waddenzee te kunnen volgen. Dit rapport beschrijft de tussentijdse resultaten, 11 jaar naar sluiting. In het monitorprogramma is de nadruk gelegd op veranderingen in de bodemfauna die jaarlijks en vanaf 2002 in het najaar bemonsterd worden. In 2016 zijn aanvullende bemonsteringen uitgevoerd. In dat jaar is de visgemeenschap herbemonsterd, zijn additionele bodemmonsters genomen gericht op het bemonsteren van de wat grotere organismen, zijn de karakteristieken van het bodemoppervlak in kaart gebracht en is de visserijdruk in het gebied berekend. Voorlopige resultaten laten zien dat in de open geulen garnalenvisserij heeft plaatsgevonden gedurende de hier bestudeerde periode en dat in de gesloten geulen geen visserij heeft plaatsgevonden na 2005. Sluiting van de geulen heeft nog niet geleid tot vestiging van biogene structuren. Wel is de soortenrijkdom toegenomen en hebben er zich subtiele veranderingen in bodemdiersamenstelling voorgedaan. Vanwege de beperkte hoeveelheid gegevens was het niet mogelijk om uitspraken te doen over veranderingen in de vispopulatie