Acronym NA
Category
Fisheries
Title Tettheter av makrell og sild i not under kommersielt fiske - Densities of mackerel and herring in nets during commercial fishing Programme National Programme
Instrument (FP6)
Contact Type (FP7)
Strand (Interreg)
NA
Theme (FP7)
Activity Area (FP6)
Regional Area (Interreg)
Action (COST)
NA
Specific Programme (FP7)
NA
Funding source National Coordinator Maria Tenningen Coordinator email maria.tenningen@imr.no
Coordinator institution
IMR - Institute of Marine Research (Norway)
Institutions involved
NA - Liegruppen AS (Norway) ,
Start year 2011 End year 2014 Funding (€) € 168,540 Website https://www.fhf.no/prosjekter/prosjektbasen/900688/ Summary Slipping, where fish are released from the net while still in water, is used to adjust catch size or increase catch value in many purse seine fisheries. High fish densities before slipping have been shown to result in high mortality and stress in the released fish and there is currently a discussion in Norway on how late in the fishing process that slipping may be accepted. There are currently no available estimates of fish densities inside the net during purse seining or any practical methods for monitoring the catches or the net during commercial fishing making the regulation of slipping difficult. In this study a method for monitoring net volume during seining was developed. Net volume provides an indirect estimate of school density if the catch size is known, assuming that the net volume is the main factor that determines school density. Hence an indication of the point when fish densities reach critically high levels can be obtained. Improved understanding of net behaviour will also provide a useful tool for technological development towards efficient and environmentally friendly purse seining.
The aims of this project are first to estimate the enclosed volume of the purse seine during the hauling process using omnidirectional sonar and acoustic positioning transponders attached to the net. Secondly, the enclosed volume as measured in several commercial purse senine catches and catch biomass were used to estimate fish densities in the net and its change as the net is hauled. Density estimates are compared to estimates of herring and mackerel mortality from existing crowding experiments and the effects of slipping during the hauling access considered.
Keywords
Fish;
Catch;
Herring;
Mackerel;
Fishing technology;
Purse seine;
Gear technology;
Marine Region
41
Norwegian Sea (27.IIa)
13
Northern North Sea (27.IVa)
2
Marine Region Map
