Implications of fisheries during the spawning season for the sustainable management and recovery of depleted fish stocks: a conceptual framework

Fishing during the spawning season may negatively affects the reproductive potential and reproductive dynamics of exploited fish stocks due to a variety of mechanisms such as the disturbance of the natural spawning behaviour, effects on the age, size and sex composition of the spawning population and effects on the population genetics. The effect may differ between species in relation to the spawning strategy and population dynamic characteristics. Based on first principles of reproductive biology, population biology and fishing methods, a theoretical framework is developed on the effects of fishing during the spawning period. This framework is used to structure a review of the available scientific evidence. Implications of the findings on the recovery of depleted fish stocks and the sustainability of exploitation will be discussed and illustrated for a selection of North Sea fish stocks (flatfish, roundfish and pelagic)

Implications of fisheries during the spawning season for the sustainable management and recovery of depleted fish stocks: life history characteristics of several North Sea species

Fish traders and NGOs have put the idea forward that in order to not disturb the spawning process and hence improve the reproductive success of a fish population one should stop fishing during the spawning period. This idea has resulted in the project “Vis & Seizoen”. Within this project a theoretical framework is being developed to examine the possible effect of fishing during the spawning season. This is the first report within the project. It presents a summary of the life history characteristics that are related to the reproduction of nine important commercial fish species

De lege zee: feit of fictie? Bespiegelingen over duurzaam visserijbeheer

De centrale vragen bij deze rede zijn: Hoeveel vis kan de zee produceren en hoe kan deze vis op een duurzame manier worden geoogst. Een beschouwing over visserijdruk, ontwikkeling van de biomassa, ecosysteemeffecten van de visserij, visserijbeheer, uitmondend in de vraag: lege zee, feit of fictie en de betekenis voor onderwijs en onderzoe

Effects of fishing during the spawning period: implications for management

Avoidance of fishing during the spawning season has been proposed as a contribution to achieving sustainable exploitation. Here we review the biological effects of fishing during the spawning period and explore their implication on sustainable management. A distinction will be made between direct mortality and indirect effects. The latter will review how fishery disturbance will affect the physiology and behaviour. Based on the results, a classification scheme is presented of the vulnerability for fisheries during the spawning period. Finally the implications for the population dynamics and fisheries management are discussed

Effort allocation of the Dutch beam trawl fleet in response to a temporarily closed area in the North Sea

The spawning stock of North Sea cod is at a historic low level and immediate management measures are needed to improve this situation. As a first step, the European Commission in 2001 closed a large area in the North Sea between February 15 and April 30 to all cod related fishing fleets in order to protect the spawning population. The closed area comprised important fishing grounds of the beam trawl fleet fishing for flatfish. In this paper the response of the Dutch fleet (components 225-300hp and >300hp) is analysed using data from EU-logbooks and from position recordings from the Vessel Monitoring System. No change was observed in the fleet of small beam trawlers. The fleet of large vessels displaced its activity to fishing grounds in the North Sea outside the closed areas, and to fishing grounds outside the North Sea. In the North Sea, beam trawling concentrated along the borders of closed areas and the Plaice Box. In the first week after the closure the number of trips in the open area doubled. Coinciding with this increase, the catch rate, expressed as revenue per hp-day, decreased. After the area was re-opened, the catch rate was exceptionally high but decreased to the normal level in the 2nd - 3rd week. The change in catch rate in relation to the change in fishing effort indicated that competitive interactions (in particular interference interactions) occurred among vessels. The implication of the observed fleet response is discussed against the background of the objective of the management measure to protect cod and the broader objective of the Common Fisheries Policy of ecosystem management. It is concluded that it is unlikely that cod has benefited from the area closure. Furthermore, the closure may have had a negative impact on the rate of discarding of demersal species and a negative impact on vulnerable components of the ecosystem (e.g. skates, long lived benthic species) due to an increase in trawling activities in certain area

De evolutionaire dimensie van duurzaam visserijbeheer

Dit rapport behandelt de evolutionaire consequenties van visserij en de implicaties hiervan voor het duurzaam beheer. Visserij verhoogt de kans dat vissen worden weggevangen voordat ze volwassen worden en zich kunnen voortplanten. Dit betekent dat de dieren die genetisch geprogrammeerd zijn om op jongere leeftijd volwassen te meer nakomelingen zullen produceren dan dieren die pas op latere leeftijd volwassen worden. Een andere eigenschap die beïnvloed kan worden is de voortplantingsinspanning (aantal eieren) en de groeisnelheid. Dieren die meer eieren produceren zijn in het voordeel. Een verlaging van de geslachtsrijpe leeftijd en een verhoging van de voortplantingsinspanning resulteert in een afname van de groeisnelheid. Visserij leidt dus tot verschuivingen in de genetische eigenschappen (evolutionaire veranderingen) van de geëxploiteerde bestanden. In dit rapport wordt een overzicht gegevens van de huidige wetenschappelijk inzichten in de door de visserijgeïnduceerde evolutie en de implicaties die dit heeft voor het visserijbeheer. Speciale aandacht wordt gegeven aan de beschikbare kennis over Noordzee platvis en de mogelijkheden die er zijn om op basis van deze kennis tot een Evolutionair Impact Assessment voor deze bestanden te komen

Biodiversity of the high seas. Final Report Lot 1

Human activities in the areas outside national jurisdiction (High Seas and the Area) are increasing and may threaten marine biodiversity. This report presents a review of human activities and their potential impact on biodiversity of the high seas. For each activity, the technical details, the extent and spatial distribution of the activity and their socioCeconomic importance is described and the potential impact on marine biodiversity is analysed