The capability of square-meshes and fixed-shape meshes to control codend size selection

Trawl codends are commonly made of diamond-mesh netting. However, diamond-mesh codends vary in mesh geometry along its length and during fishing due to catch build up. This introduces variability in the size selection process. This phenomenon compromises the rationality of regulating exploitation patterns in trawl fisheries through adjustments in codend mesh size. One technical solution often applied to achieve more welldefined size selection is turning the codend netting 45 degrees (square-mesh). However, there is a lack of evidence that square-mesh codends result in more constant size selectivity. Therefore, we aimed at quantifying the variability in size selection in square-mesh codends. We tested the size selectivity of three codends; a standard square-mesh codend, and two rigid codends where mesh geometries were fixed in diamond shape with an opening angle of 60◦ and square shape, respectively. The two rigid codends were used to establish baselines with limited variability in size selection. The size selectivity of these codends was compared to results - previously obtained for a standard diamond-mesh codend. Using Atlantic cod (Gadus morhua) as a case study, we demonstrated that the standard square-mesh codend had significantly larger variability in size selection compared to the fixed diamond-mesh codend. Moreover, we found no evidence that the standard square-mesh codend had lower variability in size selection than a standard diamond-mesh codend with same mesh size. These results demonstrate that the use of standard square-mesh codends is not sufficient to reduce variability in codend size selection. Additionally, we demonstrate that the sizes of fish retained is strongly dependent on mesh shape and openness. We conclude that a profound re-thinking over codend designs is required in order to achieve better control of size selection in trawl fisheries

Ghost fishing efficiency by lost, abandoned or discarded pots in snow crab (Chionoecetes opilio) fishery

Marine pollution by lost, abandoned or otherwise discarded fishing gear (ALDFG) often has negative impact on the ecosystem through plastic pollution and continuous capture of marine animals, so-called “ghost fishing”. ALDFG in pot fisheries is associated with high ghost fishing risk. The snow crab (Chionoecetes opilio) pot fishery is conducted in harsh weather conditions increasing the risk of fishing gear loss. Due to plastic materials used in the pot construction, lost gear can most likely continue fishing for decades. This study presents a method to quantify ghost fishing efficiency relative to catch efficiency of actively fished pots. On average, the ghost fishing pots captured 8.29 % (confidence intervals: 4.33–13.73 %) target-sized snow crab compared to the actively fished pots, demonstrating that lost pots can continue fishing even when the bait is decayed. Given the large number of pots lost each year, the ghost fishing efficiency is a considerable challenge in this fishery.publishedVersio

Ulv i Danmark - konflikter og muligheder for turismeforvaltningen : resultater af et litteraturstudie og en eksperimenterende kvantitativ spørgeundersøgelse

I 2012 fandt man for første gang i over 200 år beviser på, at ulven igen var på vej tilbage til de danske landskaber. Beviserne bestod af kadaveret af en ulv, som blev fundet i Hanstholm klitplantage, der er en del af Nationalpark Thy. Ulven er kendt for at være med til at skabe sociale konflikter, hvilket også ses i dagens Danmark. For Nationalpark Thy kan ulvens tilbagevenden være både positiv og negativ set i forhold til besøgsantallet. Gæster kan enten vælge Thy over andre nationalparker, da man her har muligheden for at se et af Danmarks mest omdiskuterede dyr, mens andre fravælger at besøge parken fx pga. frygt for ulve eller en generel negativ attitude til ulv. Opgaven er todelt. Den første del består af et grundigt litteraturstudie om ulven og hvad der kan forventes af konflikter med en reetablering af ulv i Danmark. Litteraturstudiet viste, at der er god mulighed for, at ulven kan trives i Danmark, da der er gode forhold for en generalist som ulven. Ulven kan i sin udbredelse stoppes af infrastruktur som veje og bygninger. Ulven har i andre lande været omdrejningspunkt for flere store konflikter, som også kan findes i dagens Danmark. Bl.a. konflikter ved prædation på husdyr og adfærdsændringer i forbindelse med frygt, om ikke at turde gå alene i skoven. Det er dog svært, at sige hvordan danskerne vil agerer, når eller hvis ulven øges i antal. En af metoderne til at prøve at forudse hvordan danskerne vil agerer, er ved at sammenligne Wildlife Value Orientation med lande, hvor man har oplevet samme form for reetablering som fx Tyskland, Norge og Sverige. I Danmark er størstedelen af befolkningen distanced eller mutualist, hvor man i Tyskland har en utilitarian Wildlife Value Orientation. Holdningen til ulve kan spænde bredt, og der er derfor vigtigt, at forvaltningen har et indgående kendskab til, hvilke situationer som kan forventes, og hvad forvaltningen i andre lande har gjort for, at dæmpe konflikterne. Anden del af opgaven består af en analyse af det udsendte spørgeskema. Spørgeundersøgelsen består af selvrekrutterede respondenter fra hele landet (N=422). Respondenterne er fundet gennem facebookgrupper og gennem udsendelse via e-mail. Spørgeskemaanalysen er opdelt i tre aspekter: et følelsesaspekt, hvor frygt er i fokus, et attitudeaspekt, hvor holdningen til ulve i Danmark er undersøgt og et aspekt hvor adfærdsintentionen i forhold til, om turisterne ville ændre deres opfattelse af Nationalpark Thy som feriedestination ved tilstedeværelsen af ulve er undersøgt. Der blev i analysen fundet en sammenhæng mellem alle de tre aspekter. sammenhængen kan betyde, at folk som her bange for ulve og folk som generelt har en negativ attitude overfor ulve kan være tilbøjelige til at fravælge Nationalpark Thy som feriedestination. På modsat side, kan ulven for de som har en positiv attitude over for ulve i Danmark, være mere tilbøjelig til at besøge nationalparken netop pga. ulve. Desuden blev der fundet sammenhæng mellem frygt for ulve og attituden til ulve. Frygten for ulve var signifikant større hos kvinder, hos folk med kæledyr, hos folk med mindre naturinteresse og hos folk som frygter andre dyr. Da der er så forskellige holdninger til og opfattelser af ulve, er turismeforvaltningen i Nationalpark Thy og andre steder, hvor samme situation kan opstå fx ved Nationalpark Vadehavet eller ved Nationalpark Mols Bjerge, nødt til at tage stilling til, hvilken målgruppe man ønsker at tiltrække. Desuden må den information, som udgives og den skiltning, som må opsættes være tilpasset de forskellige gruppers syn og forudsætninger. Studiet anses at være et indledende studie, og skal følges op af andre. Videre forskning bør også omfatte udenlandske turister, da der ofte kommer turister fra bl.a. Tyskland, Sverige og Norge i nationalparkerne

Ulv i Danmark - konflikter og muligheder for turismeforvaltningen : resultater af et litteraturstudie og en eksperimenterende kvantitativ spørgeundersøgelse

Masteropgave omhandelde ulvekonflikter i Danmark, med fokus på konflikter og muligheder for turismen i Nationalpark Thy.I 2012 fandt man for første gang i over 200 år beviser på, at ulven igen var på vej tilbage til de danske landskaber. Beviserne bestod af kadaveret af en ulv, som blev fundet i Hanstholm klitplantage, der er en del af Nationalpark Thy. Ulven er kendt for at være med til at skabe sociale konflikter, hvilket også ses i dagens Danmark. For Nationalpark Thy kan ulvens tilbagevenden være både positiv og negativ set i forhold til besøgsantallet. Gæster kan enten vælge Thy over andre nationalparker, da man her har muligheden for at se et af Danmarks mest omdiskuterede dyr, mens andre fravælger at besøge parken fx pga. frygt for ulve eller en generel negativ attitude til ulv. Opgaven er todelt. Den første del består af et grundigt litteraturstudie om ulven og hvad der kan forventes af konflikter med en reetablering af ulv i Danmark. Litteraturstudiet viste, at der er god mulighed for, at ulven kan trives i Danmark, da der er gode forhold for en generalist som ulven. Ulven kan i sin udbredelse stoppes af infrastruktur som veje og bygninger. Ulven har i andre lande været omdrejningspunkt for flere store konflikter, som også kan findes i dagens Danmark. Bl.a. konflikter ved prædation på husdyr og adfærdsændringer i forbindelse med frygt, om ikke at turde gå alene i skoven. Det er dog svært, at sige hvordan danskerne vil agerer, når eller hvis ulven øges i antal. En af metoderne til at prøve at forudse hvordan danskerne vil agerer, er ved at sammenligne Wildlife Value Orientation med lande, hvor man har oplevet samme form for reetablering som fx Tyskland, Norge og Sverige. I Danmark er størstedelen af befolkningen distanced eller mutualist, hvor man i Tyskland har en utilitarian Wildlife Value Orientation. Holdningen til ulve kan spænde bredt, og der er derfor vigtigt, at forvaltningen har et indgående kendskab til, hvilke situationer som kan forventes, og hvad forvaltningen i andre lande har gjort for, at dæmpe konflikterne. Anden del af opgaven består af en analyse af det udsendte spørgeskema. Spørgeundersøgelsen består af selvrekrutterede respondenter fra hele landet (N=422). Respondenterne er fundet gennem facebookgrupper og gennem udsendelse via e-mail. Spørgeskemaanalysen er opdelt i tre aspekter: et følelsesaspekt, hvor frygt er i fokus, et attitudeaspekt, hvor holdningen til ulve i Danmark er undersøgt og et aspekt hvor adfærdsintentionen i forhold til, om turisterne ville ændre deres opfattelse af Nationalpark Thy som feriedestination ved tilstedeværelsen af ulve er undersøgt. Der blev i analysen fundet en sammenhæng mellem alle de tre aspekter. sammenhængen kan betyde, at folk som her bange for ulve og folk som generelt har en negativ attitude overfor ulve kan være tilbøjelige til at fravælge Nationalpark Thy som feriedestination. På modsat side, kan ulven for de som har en positiv attitude over for ulve i Danmark, være mere tilbøjelig til at besøge nationalparken netop pga. ulve. Desuden blev der fundet sammenhæng mellem frygt for ulve og attituden til ulve. Frygten for ulve var signifikant større hos kvinder, hos folk med kæledyr, hos folk med mindre naturinteresse og hos folk som frygter andre dyr. Da der er så forskellige holdninger til og opfattelser af ulve, er turismeforvaltningen i Nationalpark Thy og andre steder, hvor samme situation kan opstå fx ved Nationalpark Vadehavet eller ved Nationalpark Mols Bjerge, nødt til at tage stilling til, hvilken målgruppe man ønsker at tiltrække. Desuden må den information, som udgives og den skiltning, som må opsættes være tilpasset de forskellige gruppers syn og forudsætninger. Studiet anses at være et indledende studie, og skal følges op af andre. Videre forskning bør også omfatte udenlandske turister, da der ofte kommer turister fra bl.a. Tyskland, Sverige og Norge i nationalparkerne.In 2012 - for the first time in over 200 years - evidence was discovered that the wolf was returning to the Danish countryside. The evidence consisted of the carcass of a wolf, found in Hanstholm Klitplantage, which is part of Thy National Park. Attitudes toward the wolf are divisive, and have been known to cause social conflict in Denmark. The return of wolves has both positive and negative attributes for Thy National Park in relation to their visitor counts. Guests can either choose Thy over other national parks, as they now have the opportunity to see one of Denmark's most controversial animals, while others may opt out of visiting the park, e.g. due to a fear of wolves or a general negative attitude to the wolf. The survey is two-fold. The first part consists of a thorough literature review on the wolf and what conflicts can be expected with the recolonization of wolves in Denmark. The literature review showed that there is a good chance that wolves can thrive in Denmark, as there are good conditions for a generalist predator like the wolf, although the distribution of the wolf may be stopped by infrastructure such as roads and buildings. Elsewhere, the wolf has been the focal point for several major conflicts, which can now be found in Denmark. Examples of conflicts are predation on livestock and behavioral changes associated with fear, e.g. people now not daring to walk alone in the woods. However, it is difficult to say how the Danes will act when or if the wolf increases in number. One way to try to predict how the Danes will act is by comparing Wildlife Value Orientation with countries that have experienced the same kind of recolonization, such as Germany, Norway and Sweden. In Denmark the majority of the population is displayed as distanced or mutualist, where Germany has a utilitarian Wildlife Value Orientation. Attitudes towards wolves can range widely, and it is therefore important that the National park’s management have a thorough knowledge of the situations that can be expected and what the management in other countries have done to curb the conflicts. The second part of the survey consists of an analysis of the questionnaire that was distributed. The survey consists of self-recruited respondents from across the country (N = 422). Respondents were found through facebook groups and by e-mail. The questionnaire analysis is divided into three aspects: an emotional aspect where the concentration is on fear, an attitude aspect where the attitude towards wolves in Denmark are examined, and a behavioral intention aspect, where intentions and perceptions of potential tourists to Thy National Park are studied. The analysis found a correlation between all three aspects. The association may mean that people who are afraid of wolves and people who generally have a negative attitude towards wolves may be inclined to opt out of Thy National Park as a holiday destination. On the contrary, for those who have a positive attitude towards wolves in Denmark, the wolf could become the main attraction in visiting the national park. Correlation were also found between fear of wolves and attitude to wolves. The fear of wolves was significantly greater in 3 women, in people with pets, in people with less interest in nature, and in people who fear other animals. Since there are many different attitudes and perceptions towards wolves, tourism management in Thy National Park (and other places where the same situation may occur, for example in Wadden Sea National Park or in Mols Bjerge National Park), need to decide which visitors they want to attract. Furthermore, the information that is published and the signage that must be done has to be adjusted to the different groups. The study is considered to be a preliminary study, and to be followed by others. Further research should also include foreign tourists, as tourists in the national parks often come from either Germany, Sweden and Norway.M-REI

Selectivity in snow crab (<i>Chionoecetes opilio</i>) pot fishery: Effect of escape gap shape and size for conservation of fishery resources

Conical pots are commonly used fishing gear for capturing snow crab (Chionoecetes opilio). In these fisheries, optimal snow crab size selection is important for reducing unintended mortality of undersized individuals aiming at conserving fisheries resources and reducing sorting time onboard fishing vessels. Size selection in snow crab pot fisheries commonly takes place through pot netting meshes during deployment. The diamond mesh netting has varying opening angles affecting retention of snow crab of different sizes, and often large proportions of catches consist of undersized crab challenging natural resource conservation. Some commercial snow crab fisheries use rigid escape gaps in addition to mesh selection to improve size selectivity. In this study, we predict the size selection potential of escape gaps with different shape and size and investigated whether such additional size selection mechanism can have a potential to improve selectivity compared to mesh selection. Results showed that circular escape gaps have potential to provide sharper size selection compared to netting meshes and thus could be used to limit the capture of undersized snow crab which is relevant for management and conservation of snow crab resources. However, a similar positive effect cannot be obtained to the same extent with elliptical and rectangular escape gaps

Are rigid sorting devices necessary to control size selectivity in demersal trawl fisheries?

Diamond mesh codends are the most common size selectivity devices in trawls for releasing bycatch and undersized individuals. However, codend selectivity can vary due to the flexibility of the netting meshes, making discrimination by size between retained and released fish difficult to control. In some trawl fisheries, rigid sorting devices have been introduced to make size selection more controlled with sharper discrimination by size. However, the resulting size selectivity often does not show a sharp size selection. In the present study, we tested and compared the size selectivity performance of two “diamond-mesh codend designs” in the Barents Sea gadoid-trawl fishery: a four-panel codend, which was more rigid than a traditional two-panel codend design due to the additional selvedges, and a fully rigid codend design, that included a metal frame. The aim was to investigate the effect of added codend rigidness on the size selectivity of cod (Gadus morhua), haddock (Melanogrammus aeglefinus) and redfish (Sebastes spp.). In addition, the obtained results were compared to earlier research on size selectivity in this fishery including codends with different levels of rigidness and sorting grids. The results demonstrated that using a fully rigid codend did not result in a sharper size selectivity compared to a four-panel codend. Further, there was no indication that a rigid sorting grid makes size selectivity sharper than what can be obtained with a four-panel diamond mesh codend alone. There was also no proof that other codend stabilizing mechanisms such as shortened lastridge ropes could make the size selection sharper compared to the four-panel codend