Publicaties

An overview of the pulse logbook data collected in 2017-2019

Rijssel, Jacco C. van; Rijnsdorp, Adriaan

Samenvatting

Knowledge on how fishers exploit their fisheries resources is important for understanding how fishing affects the population dynamics of the exploited species and how the fishery may affect the ecosystem. The introduction of a new gear may affect the way fishers deploy their gear in space and time. We compared the behaviour of pulse trawl vessels to the behaviour of traditional beam trawl vessels. Because the pulse logbook monitoring is still ongoing, the results are preliminary and will be updated when the complete data set will become available. The logbook data set analysed comprised catch and effort information per tow collected between 1 January 2017 and 31 December 2019. The results were compared with an analysis of logbook data of traditional beam trawl vessels collected between 2000 - 2005. This report repeated the analyses of the previous report (data from 01/01/2017-30/08/2018) and found very similar results regarding the differences between fishing patterns of the pulse trawl and the traditional beam trawl. In total, after quality filtering, data of 141,000 hauls from 75 pulse vessels were investigated. The previous study showed that pulse trawl (PT) and traditional beam trawl (BT) vessels had similar fishing patterns with alternating periods of searching, or sampling, for fishing grounds and exploitation of fishing grounds. The main differences with the results of the previous report is that a longer time series and therefore more data has been used to analyse the logbooks. Because of this similarity, the results of these analyses will not be reported in this provisional report but will be discussed in the final report. The cpue (catch per unit effort) of sole follows a clear seasonal pattern and seems to decrease slightly through time. Also the number of logbook received by fishermen clearly decreased as a result of the ban on pulse fisheries by the EU. The logbook data provide detailed information on what happens on the local fishing grounds which is fundamental to assess the impact of the pulse trawl fishery and beam trawl fishery on the fisheries resources and on the benthic ecosystem. The study of the total pulse fleet provides a unique data set to study not only the dynamics of the whole fleet, including the interactions among pulse vessels, but also provides a solid basis to study competitive interactions with other fisheries. The next step is to study the weekly fishery patterns of the fleet as a whole and to study the interaction between vessels.