Gill net fisheries: Development of alternative management approaches (STELLA)


Stellnetze im Greifswalder Bodden (c) Thuenen-Institut/ Daniel Stepputtis
Stellnetze im Greifswalder Bodden (© Thuenen-Institut/ Daniel Stepputtis)

Development of alternative management approaches and fishing gear and techniques towards minimizing conflicts in gill net fisheries and conservation objectives and subjects of protection in the EEZ of the Baltic Sea (STELLA)

Previous approaches to mitigate the potential conflict between passive fisheries and conservation goals were limited to the development and testing of possible measures. These measures include the discussed exclusion of fisheries from certain areas or a reduction of effort. Since currently the actual effort is not known, the success of such measures can hardly be estimated reliably. Year-round closing of larger areas would have considerable socio-economic consequences, not only for the fishing industry but also for directly (processing, maintenance, port industries) or indirectly (tourism) dependent industries and trades. Studies concerning the increase of acceptance of conservation measures by the fisheries have so far rarely been conducted but are vital for the successful introduction. Such studies could, for example, refer to the improvement of the data situation or the drive systems for the use of modified or alternative fishing gears.

Background and Objective

The overall objective of this project is to make significant progress towards resolving existing or potential conflicts between the activities of passive fisheries (mainly gill-net fishing) and the conservation of marine birds and marine mammals in the German EEZ of the Baltic Sea.


In the past experiments on different modifications of gill-nets and even alternatives to gill-net use in general were conducted to reduce unwanted by-catch. To reduce the by-catch of porpoises for example the “acoustic visibility” of net-material was increased which is supposed to lead to a better detection of nets by means of the porpoise’s biosonar. Another method is the use of so-called Pingers (“startlers”) which emit a signal that is unpleasant for porpoises and thus should keep them away from gill-nets. In some areas of the Baltic the use of Pingers is mandatory, but not for all fleet segments. However, the long-term effectiveness of the hitherto used Pingers is not guaranteed. Uncontrolled failure of devices can occur and result in the animals being lead into the “silent” net areas. At the same time the possibility of familiarisation effects is being discussed. Additionally, the ‘startlers’ could further reduce the available habitat and therefore be contrary to the conservation goals. Consequently, work is being conducted on an alternative Pinger concept where the porpoises are being warned by species-specific signals (PAL, current study under leadership of the Thuenen Institute of Baltic Fisheries). Regarding the native and migratory marine birds for which the Baltic represents an important moulting-, roosting- and breeding-area, there are up to now no differentiated concepts to decrease by-catch which have proven to be practical in commercial passive fisheries – except for a blanket exclusion of fisheries.


Involved Thünen-Partners

Funding Body

  • Federal Agency for Nature Conservation (BfN)
    (national, öffentlich)


11.2016 - 1.2020

More Information

Projekt type:
Project funding number: 3516 82 1300
Funding program: BMUB - Umweltforschungsplan
Project status: ongoing


hits: 9

  1. Chladek J-C, Stepputtis D, Hermann A, Ljungberg P, Rodriguez-Tress P, Santos J, Svendsen JC (2021) Development and testing of fish-retention devices for pots: transparent triggers significantly increase catch efficiency for Atlantic cod (Gadus morhua). ICES J Mar Sci 78(1):199-219, DOI:10.1093/icesjms/fsaa214
  2. Meyer S, Krumme U (2021) Disentangling complexity of fishing fleets: using sequence analysis to classify distinguishable groups of vessels based on commercial landings. Fish Manag Ecol 28(3):268-282, DOI:10.1111/fme.12472
    pdf document (limited accessibility) 2034 kb
  3. Kratzer I (2021) Gillnet modifications to reduce bycatch of harbor porpoises. DTU Aqua National Institute of Aquatic Resources, 172 p, Lyngby, Techn Univ of Denmark, Section for Ecosystem Based Marine Management, PhD Thesis
  4. Kratzer I, Brooks ME, Bilgin S, Ozdemir S, Kindt-Larsen L, Larsen F, Stepputtis D (2021) Using acoustically visible gillnets to reduce bycatch of a small cetacean: first pilot trials in a commercial fishery. Fish Res 243:106088, DOI:10.1016/j.fishres.2021.106088
  5. Chladek J-C, Stepputtis D, Hermann A, Kratzer I, Ljungberg P, Rodriguez-Tress P, Santos J, Svendsen JC (2021) Using an innovative net-pen-based observation method to assess and compare fish pot-entrance catch efficiency for Atlantic cod (Gadus morhua). Fish Res 236:105851, DOI:10.1016/j.fishres.2020.105851
  6. Barz F, Eckardt J, Meyer S, Kraak SBM, Strehlow HV (2020) "Boats don't fish, people do"- how fishers' agency can inform fisheries-management on bycatch mitigation of marine mammals and sea birds. Mar Policy 122:104268, DOI:10.1016/j.marpol.2020.104268
  7. Schwermer H, Barz F, Zablotski Y (2020) A literature review on stakeholder participation in coastal and marine fisheries. In: Jungblut S, Liebich V, Bode-Dalby M (eds) YOUMARES 9 - The oceans: our research, our future : Proceedings of the 2018 conference for YOUng MArine RESearcher in Oldenburg, Germany. Cham: Springer Open, pp 21-43, DOI:10.1007/978-3-030-20389-4_2
    pdf document (limited accessibility) 999 kb
  8. Kratzer I, Schäfer I, Stoltenberg A, Chladek J-C, Kindt-Larsen L, Larsen F, Stepputtis D (2020) Determination of optimal acoustic passive reflectors to reduce bycatch of odontocetes in gillnets. Front Mar Sci 7:539, DOI:10.3389/fmars.2020.00539
    pdf document (limited accessibility) 1067 kb
  9. Hermann A, Chladek J-C, Stepputtis D (2020) iFO (infrared Fish Observation) - An open source low-cost infrared underwater video system. HardwareX 8:e00149, DOI:10.1016/j.ohx.2020.e00149
    pdf document (limited accessibility) 4103 kb