Behaviour of grey seals (Halichoerus grypus) and their prey in and near set traps

The seal populations of the Baltic Sea Area were at historically low levels in the 1970’s, due to two factors. The first was an extensive hunt and the second was emissions of organochlorines, which affected the reproductive abilities of the females. Laws and regulations were set in force to improve the marine environment and from the early 1990’s the populations of the grey seal (Halichoerus grypus), the harbour seal (Phoca vitulina) and the ringed seal (Pusa hispida) have recovered. It is a success for the management of the Baltic Sea Area environment that the seal populations have increased. Coupled with the increase of the populations, is also an increase of conflicts with the inshore fisheries. The seals frequenting the fishing gear takes fish and damage gear. It is mainly the grey seal which is the culprit and it is predominantly males. These males have been proven to be specialists. Two studies were conducted to learn more about the behaviour of seals and of their prey. The first study investigated the pattern of seal visits in the middle chamber of a herring pontoon trap. A camera filmed the seals which entered and the seals were identified. There were almost 1400 visits by 12 individuals. Of all visits, 84 % took place within 5 minutes of each other. Of all visits, 3.7 % were concurrent visits, i.e. two males inside the middle chamber at the same time. By studying these visits in detail, it could be concluded that there was a dominance hierarchy among the seals in the trap. A simulation of the visits was executed to examine whether the proportion of concurrent visits was random or non-random. The simulations used the same distribution pattern of the realized visits. If the visits had been random, then c 9.5 % of them would have been concurrent. This suggests that there is a pattern to their visits. The second study investigated the effect of a Seal Exclusion Device (SED) on seal visits and on catch. The experiment was conducted during two years. In 2012, using a SED with a diamond mesh and in 2016 using two SEDs; the diamond mesh and a square mesh - with the entire frame rotated 45°. The expectation was that the SEDs would reduce the number of seal visits, increase the catch and possibly deter larger fish from entering. In 2012, the diamond mesh had an effect on the size of trout, with larger trout entering the control trap, whereas large salmon were not affected by the presence of the SED. In 2016, larger salmon were caught in the traps with a SED. There was no significant result regarding the catch of trout, possibly due to small samples. The number of seal visits in both sets of experiments were too low to be able to draw any conclusions regarding presence of seals. The SEDs did not have any effect on the quantity of caught fish

Salmonids and grey seals (Halichoerus grypus)

In the 1970’s, the seal populations of the Baltic Sea Area were at historically low levels. They have recovered and increased since then. The increase of the seal populations is a success for the management of the Baltic Sea Area environment. It has also meant an increase in number of interactions with coastal fisheries. Seals take fish and damage fishing gear. Three studies were carried out with the purpose of contributing to a sustainable fishery and fewer interactions between seals and fishers. The first study compared the effect two different Seal Exclusion Devices (SEDs) had on the catch and on seal visits. The SEDs used were a diamond mesh SED and a square mesh SED, with the frame rotated 45°. They were compared with a control, an open frame. The expectation was that using SEDs would reduce the number of seal visits, increase the catch and deter larger fish from entering. Larger salmons (Salmo salar) were caught in the traps with selection panels. For brown trout (Salmo trutta), there was no difference in size of fish between the SEDs. Neither of the SEDs had any effect on total catch or catch per unit effort. The number of seal visits were too low to be able to draw any conclusions regarding presence of seals. The second study examined the efficiency of selection panels in a pontoon trap for salmon and whitefish. One control and two experimental traps were used. The mesh in the control trap had 35 mm bar length. The selection panel was square mesh with 50 mm bar length. In one of the experimental traps, the selection panel covered 30 % of the inner netting. In the other, it covered 100 %. The results showed that proportionally more fish of commercial size were caught in traps with selection panels. Using selection panels contributes to a sustainable fishery. The third study analysed a series of visits by seals in the middle chamber of a herring pontoon trap. Visiting seals were filmed in the middle chamber. Roughly, 1 400 visits by 12 seals were recorded. Of all visits, 3.5 % were overlapping visits, i.e. two seals inside the middle chamber at the same time. Forty simulations of random visits were performed resulting in an average of 7.1 % overlapping visits. There was a significant difference between the actual overlapping visits and the simulated. This suggests that the seals avoided swimming in when another seal was presen

Onnistunut verkkotiedottaminen tapahtuman aikana

Tavoitteenani opinnäytetyössäni on selvittää, miten tapahtumanaikaisessa verkkotie-dottamisessa onnistutaan. Pohdin työssäni millaista verkkotiedottaminen on, mitä sillä voidaan saavuttaa ja miksi tapahtuman aikaista verkkotiedottamista tarvitaan. Opinnäytetyössäni esittelen erilaisia alustoja, joilla verkkotiedottamista kannattaa harjoittaa. Viestintää tehdään vastaanottajalle eli yleisölle. Käyn läpi miten ja miksi tapahtuman yleisö kannattaa ottaa osaksi tapahtuman aikaista verkkotiedottamista. Huomio keskittyy erityisesti erilaisiin sosiaalisen median muotoihin. Opinnäytetyöni toiminnallinen osuus käsittelee Torniossa vuonna 2013 järjestettyä Radiofestivaalit- tapahtumaa. Toimin tapahtuman ajan verkkotiedottajana ja ana-lysoin omia kokemuksiani tuolta ajalta. Esittelen työssäni käytössämme olleet alustat ja sen, mitä niillä saimme aikaan. Tapahtumanaikaisen verkkotiedottamisen on oltava nopeaa ja tehokasta. Tiedottajan on otettava huomioon tapahtuman kohderyhmä, tapahtuman luonne ja puntaroitava mikä tieto on tapahtuman onnistumisen kannalta oleellista.In this thesis study I focus on the process of implementing successful web communi-cation during an event. I discuss what web communication during an event actually entails and what can be achieved with that and why it is important to communicate via web during the event after all. In this thesis I focus on introducing different kinds of social media platforms. Com-munication is made for the audience. I concentrate on one of the main questions: how and why is it important to make audience a part of web communication. I discuss various platforms that can be used and are beneficial to use in web communication. The focus here is on various platforms of social media. The practice-based part of the thesis concentrates on my own experiences in the event Radiofestivals 2013, where I was working as the web communication coordinator during the festivals. I discuss which platforms were used and what was achieved by using them. Communication during an event must be quick and effective. The information coor-dinator has to consider the target audience, the character of the event, and what kind of information is really important to disseminate for making a successful event

Seal visits 2012 and 2016

Filmed number of hours and seal visits in pontoon traps equipped with two different types of Seal Exclusion Devices, compared to a Control. The study took place in 2012 and 2016

Seal Exclusion Device in a pontoon trap for salmonids affects the size and numbers of caught fish

Year Test Seal visits (no) Frequency (visits per filmed hour) Total time in trap or by SED (mm:ss) 2012 Diamond mesh SED 1 0.01 00:07 2012 Control 6 0.01 00:54 2016 Square mesh SED 1 0.01 05:13 2016 Diamond mesh SED 0 0.00 00:00 2016 Control 0 0.00 00:00 The pontoon trap is a successful means of mitigation in the conflict between coastal fishers and seals interacting with fishing gear. It distances caught fish from seals and is considered to be seal-safe in this respect [1]. The seals have had unlimited access to one of the final parts of the trap, the middle chamber. This leads to a risk of entanglement. In Finland the pontoon trap is considered to be the main cause of seals becoming bycatch [2]. Seals also damage and stress caught fish. To prevent seals from entering the middle chamber two types of Seal Exclusion Devices (SEDs) were tested. The study used pontoon traps for salmon (Salmo salar) and brown trout (Salmo trutta). The SEDs were aluminium frames with Dyneema® yarn across the frame, in diamond or square mesh shapes. They were installed in the entrance of the middle chamber. The square mesh SED was rotated 45°. The control was an open frame. The hypothesis tested were (i) the SED would prevent seals from entering the middle chamber and (ii) the catch would increase. A negative side effect was expected. The SED would deter larger fish from entering. The collected data was the individual size of the fish and numbers of fish caught per soak day. Cameras were installed to record seal visits. The study was carried out over two years. The visits of seals were too few to draw any inferences (Table 1). No seals were bycaught in any of the middle chambers. Significantly larger salmons were caught in the trap with the square mesh SED, followed by the diamond mesh SED. It is likely that the SEDs had a retaining effect on larger salmons. For trout, significantly smaller fish were caught in the trap with the diamond mesh SED, suggesting that it was perceived as an obstacle. A possible explanation is that 44 % of the area in the diamond mesh SED was quarter or half mesh, thus creating a visual disturbance. In the square mesh SED all mesh were full and of the same size. The numbers of caught salmon and trout were significantly greater in traps with a SED, i.e. profitable from a fishers point of view. With the growing populations of seals in the Baltic it becomes increasingly more important to reduce the bycatch of seals, while not affecting the catch. A SED in a pontoon trap will also decrease stress on caught fish. References 1. Hemmingsson M, Fjälling A, Lunneryd S-G. 2008 The pontoon trap: Description and function of a seal-safe trap-net. Fish. Res. 93, 357-359. 2. Vanhatalo J, Vetemaa M, Herrero A, Aho T, Tiilikainen R. 2014 By-catch of grey seals (Halichoerus grypus) in Baltic fisheries - A Bayesian analysis of interview survey. PLoS One 9, 1-17.peerReviewe

Salmon and trout catch 2012 and 2016

Catch from 2012 and 2016 from a pontoon trap equipped with two different types of Seal Exclusion Devices. Each caught fish was weighed individually at every harvest occasion. Total catch, number of harvest occasions, Catch Per Unit Effort (CPUE) - total numbers of fish per soak day in one trap and Weight Per Unit Effort (WPUE)- weight of the catch per soak day in one trap, can be calculated from this data

Data from: Pontoon trap for salmon and trout equipped with a seal exclusion device catches larger salmons

The growing seal populations of the Baltic have led to more frequent interactions with coastal fisheries. The motivation for seals to interact with fishing gear is high. It provides high densities of fish. A successful means of mitigating the conflict is the pontoon trap. Seal visits here have been frequent. Seals have access to most parts of the trap system including the middle chamber, which is an overhead environment. Concerns have been raised about seals possible entanglement in this specific part of the trap. As a means of keeping seals from entering the middle chamber, two different Seal Exclusion Devices (SEDs) were tested. A diamond mesh SED and a square mesh SED, which was rotated 45°. The aim was to compare the functionality of the different SEDs with respect to seal deterrent abilities and catch composition. The hypothesis tested were (i) that seals would not be able to enter the middle chamber, (ii) that the catch would increase and (iii) that the SED would deter larger fish from swimming into the middle chamber. Catch data and underwater film were collected. Larger salmons were caught in traps equipped with SEDs. The SEDs did not affect the number of caught fish or the total catch per soak day

Data from: Pontoon trap for salmon and trout equipped with a seal exclusion device catches larger salmons

The growing seal populations of the Baltic have led to more frequent interactions with coastal fisheries. The motivation for seals to interact with fishing gear is high. It provides high densities of fish. A successful means of mitigating the conflict is the pontoon trap. Seal visits here have been frequent. Seals have access to most parts of the trap system including the middle chamber, which is an overhead environment. Concerns have been raised about seals possible entanglement in this specific part of the trap. As a means of keeping seals from entering the middle chamber, two different Seal Exclusion Devices (SEDs) were tested. A diamond mesh SED and a square mesh SED, which was rotated 45°. The aim was to compare the functionality of the different SEDs with respect to seal deterrent abilities and catch composition. The hypothesis tested were (i) that seals would not be able to enter the middle chamber, (ii) that the catch would increase and (iii) that the SED would deter larger fish from swimming into the middle chamber. Catch data and underwater film were collected. Larger salmons were caught in traps equipped with SEDs. The SEDs did not affect the number of caught fish or the total catch per soak day

The two Seal Exclusion Devices (SEDs) and the control frame.

<p>The diamond mesh SED, the square mesh SED and the control. The control was an open aluminium frame. The grey area in the diamond mesh SED indicates half- or quarter mesh.</p

Pontoon trap for salmon and trout equipped with a seal exclusion device catches larger salmons

<div><p>The growing seal populations of the Baltic have led to more frequent interactions with coastal fisheries. The motivation for seals to interact with fishing gear is high. It provides high densities of fish. A successful means of mitigating the conflict is the pontoon trap. Seal visits here have been frequent. Seals have access to most parts of the trap system including the middle chamber, which is an overhead environment. Concerns have been raised about seals possible entanglement in this specific part of the trap. As a means of keeping seals from entering the middle chamber, two different Seal Exclusion Devices (SEDs) were tested. A diamond mesh SED and a square mesh SED, which was rotated 45°. The aim was to compare the functionality of the different SEDs with respect to seal deterrent abilities and catch composition. The hypothesis tested were (i) that seals would not be able to enter the middle chamber, (ii) that the catch would increase and (iii) that the SED would deter larger fish from swimming into the middle chamber. Catch data and underwater film were collected. Larger salmons were caught in traps equipped with SEDs. The SEDs did not affect the number of caught fish or the total catch per soak day.</p></div