Stakeholders’ Perspectives On the Management Measures in Rapana venosa Fisheries in the Black Sea Turkish Coast

The Rapa whelk (Rapana venosa), which entered the Black Sea as an invader, has become a commercial stock and has brought many problems in its management since the 1980s. This research aimed to get a detailed idea about the views of the stakeholders of the Rapa whelk sector and to develop concrete and applicable suggestions for the sustainability of the sector. For this, first of all, all stakeholder groups were brought together and their opinions were taken. Afterward, the management measure suggestions collected from the group were evaluated by everyone through questionnaires. When the general opinions of the stakeholders were evaluated, it was seen that most of the beam trawlers argued that legal restrictions should be softened to be able to fish more while academicians and representatives of environmental organizations stated that environmentally friendly fishing gear should be designed and used to protect the marine ecosystem. The policymakers participating in the workshop think that some arrangements can be made in the current legislation, but there is no need for radical changes. Industry sector stakeholders participating in the workshop, on the other hand, think that measures that restrict their production, such as quota limitation, are not appropriate. In summary, in the study, alternative management measures were examined and their possible effects were evaluated. As a result of this study, recommendations were made for sustainable fishing of Rapa whelk.


Introduction
Rapa whelk is one of the species that is constantly on the agenda and has dilemmas because it is both an invasive species and an important source for commercial fisheries in the Black Sea (Busch et al 1999;Aydın et al. 2016, Demirel et al. 2021).Rapa whelk is a carnivorous and the most active predator of bivalves such as mussels and oysters (Lanfranconi et al. 2009;Teaca et al. 2019;Savini 2006).In the Black Sea, the amount of Rapa whelk, which has a low predator effect, increases significantly and causes a decrease in mussel and oyster stocks.This is especially important in terms of adult mussels being a food source for demersal fish and carnivorous pelagic fish (Morrisey et al. 2006).A decrease in mussel stocks may affect the nutrition of demersal fish.In addition, the decrease in primary consumers fed by filtration can create biological pollution (Seyhan et al. 2003).The fact that Rapa whelk are very voracious organisms and the absence of natural competitors and predators in the Black Sea region causes their rapid reproduction and an explosion in stocks.For this reason, in many studies, it has been stated that this species should be constantly fished and kept under control (Artüz 1989).Therefore, it appears that it is necessary to support Rapa fishing by implementing appropriate management measures (Sağlam et al. 2017).
Rapa whelk, which started to gain commercial importance in Turkey after 1985, is exported to many countries, mainly Japan, South Korea, Taiwan, and the People's Republic of China, as a frozen product after being processed in factories.According to the records of the Eastern Black Sea Exporters' Association, Turkey generated approximately $6.5 million in revenue from the export of approximately 989 tons of frozen Rapa whelk meat in 2021 (TURKSTAT 2022).The Rapa whelk sector also employs around 5000 people (Erik et al. 2020).
The gradual increase in the fishing and trade volume of Rapa whelk has led to a discussion of its effects on the environment.Since it is known that the beam trawl used in Rapa fishing damage the benthic habitat, new searches have been made for alternative fishing gear.Although the discard rate is 1-2% by weight with beam trawling (Erik and Dağtekin 2022), there are concerns about the use of this fishing gear since sensitive species such as turbot are also caught (Petrova et al. 2020).
Official regulations on Rapa whelk fishing were first introduced by the Ministry of Agriculture, Forestry and Rural Affairs -General Directorate of Protection and Control in the fishing season of [1985][1986].Afterward, new measures were taken continuously due to the changes over the years.However, many problems were encountered in the implementation of the introduced rules.For this reason, especially for the time constraints applied to the beam trawl have been changed many times (Table 1).Another change in management measures is fishing time regulation.The governing authority has tried to ban beam trawling as much as possible during the summer months.Since it is an environmentally friendly fishing method, pot fishing was tried to be encouraged during this period.However, this method was not adopted by the fishers for some reasons including low catch and high labor requirements.Similarly, experimentally successful eco-friendly beam trawl designs have not been favoured by fishers.For years, sector stakeholders have expressed their problems at stakeholder meetings.Although various issues have been resolved in this period, some problems persist.As a result, many changes have been made in Rapa fishing management in the last 40 years, but some measures have not been implemented until today.
To increase the impact of fisheries research in the Black Sea on the real economy, the results should be shared with all stakeholders.It is known that the results are not effective enough when the stakeholders are not sufficiently convinced (Dağtekin et al. 2021a).In this study, the management measures applied in Rapa fishing that the stakeholders did not agree with were examined, and the perspectives of the sector stakeholders on new possible measures were tried to be evaluated.In addition; It is aimed to answer questions such as how to choose a fishing gear, how to achieve success in the management of fisheries by considering the invasive feature of R.venosa, how to ensure minimum destruction of the ecosystem, how to ensure sustainable use of fisheries resources, and how sustainable fishing measures affect the economic situation of fishers.

Material and Method
Focus group discussions were held with Rapa whelk fishers, small-scale fishers, fishers cooperatives, fisheries management authorities, fisheries inspectors, researchers, and fisheries industry stakeholders.The workshop, first of all, it was tried to determine the general expectations of the stakeholders from the current management measures and what measures could be taken to ensure sustainability in Rapa fisheries.
This study, it was aimed to determine appropriate management measures for the sustainability of Rapa whelk fishing in Türkiye.For this purpose, on March 29, 2022, a workshop was organized with the participation of researchers from universities and research institutes, Rapa whelk fishers, small-scale fishers, cooperatives, management units, fisheries inspectors, non-governmental organizations, managers of Rapa whelk processing factories, Rapa whelk wholesalers at Central Fisheries Research Institute, Trabzon.The workshop was evaluated using the stakeholder analysis method.In the first half of the workshop, previously selected topics were discussed and potential management measures were identified to represent the views of each stakeholder.In the second stage, a questionnaire was created by listing the selected management measure options and it was determined whether the stakeholders agreed with the suggestions.The main material of the research is the primary data obtained from the stakeholders participating in the workshop through a questionnaire.Various opinions expressed by the stakeholders during the workshop that could not be obtained through the survey are also among the materials of the study.In addition to these, scientific studies such as various books, journals, articles, and both current and previous legislation related to Rapa Whelk fishing were also used.
The stakeholder analysis method constitutes the first stage of adopting a strategic management approach for the fishery sector, as in other sectors.This method aims to ensure that the management measures to be put forward provide optimum benefit for all stakeholders.The presence of many stakeholders with a high level of interaction potential in the Rapa whelk sector makes it necessary to determine the management measures to be implemented in this sector by using the stakeholder analysis method.In the first stage of the research, the stakeholders of the Rapa whelk fishing sector were determined.Afterward, a workshop was organized to bring the stakeholders together and their views on various issues were determined.In the last stage, the data obtained were analyzed and the importance levels of the management measures that can be applied in the Rapa whelk fishing sector were determined for the stakeholders (Fig. 1).Various descriptive statistical methods such as mean, standard error, frequency, and percentage were used in the analysis of the data collected from the stakeholders through the questionnaire.
In addition to the stakeholder analysis, the data of a previous study on using twin beam trawl which is frequently demanded by Rapa whelk fishers were analyzed

Spatial Regulations
Rapa whelk fishing is prohibited in areas with a radius of 500 m of the areas streams flow into the sea.
Implemented between 1985-1993 and 1996-2022 Rapa whelk fishing is prohibited in areas with a radius of 200 m of the areas streams flow into the sea.

Implemented between 1993-1996
Fishing of Rapa whelk with beam trawl is prohibited in our territorial waters in the Black Sea, from the Bulgarian border to Samsun province Yakakent district, Çayağzı Cape.

Implemented between 2002-2004
In the Black Sea; Rapa whelk fishing by diving and pot method is possible except in the territorial waters between Rumeli Karaburun and Anadolu Karaburun at the entrance of the Bosphorus.

Fishing Gear
The required features of the beam trawl: Mouth width: maximum 3 m, Mouth depth: maximum 40 cm, Bag length: maximum 2.5 m, Mesh size: minimum 45 mm.

Implemented between 1985-2006
It is obligatory to have a selective grid on the top and back of the bag, with a size of 0.5x1m (0.5 m 2 ) and a bar spacing of not less than 45 mm.

Implemented between 2001-2002
The required features of the beam trawl: Mouth width: maximum 3 m, Mouth depth: maximum 40 cm, Bag length: maximum 1 m, Mesh size: minimum 90 mm.

Implemented between 2006-2012
The required features of the beam trawl: Mouth width: maximum 3 m, Mouth depth: maximum 40 cm, Bag length: maximum 1 m, Mesh size: minimum 72 mm.

Implemented between 2012-2019
The required features of the beam trawl: Mouth width: maximum 3 m, Mouth depth: maximum 40 cm, Bag length: maximum 1.5 m, Mesh size: minimum 72 mm.

Implemented between 2019-2022
Temporal Ban Rapa whelk fishing is prohibited from 1 July to 1 August.Implemented in 1985 Rapa whelk fishing is prohibited from 15 July -31 August.
Implemented in 1986 Rapa whelk fishing is prohibited from 15 April -1 August, 1987 with beam trawl.Rapa whelk fishing is prohibited from 1 August-1 October, 1987 with all kinds fishing gears.

Implemented in 1987
Rapa whelk fishing is prohibited from 1 April -15 July, with beam trawl.Rapa whelk fishing is prohibited from 15 July -1 October with all kinds fishing gears.

Implemented between 1988-1990
Rapa whelk fishing is prohibited from 15 July -1 September with all kinds fishing gears.

Implemented between 1991-1993
Rapa whelk fishing is prohibited from 1 May -1 September, with beam trawl.Rapa whelk fishing is prohibited from 15 July -1 September with all kinds fishing gears.

Implemented between 1994-1995
Rapa whelk fishing is prohibited from 15 July -1 September with all kinds fishing gears (except diving).

Implemented between 1995-1996
Rapa whelk fishing is prohibited from 15 May -1 September, with beam trawl.Rapa whelk fishing is prohibited from 15 July -1 September with all kinds fishing gears.

Implemented in 1997
Rapa whelk fishing is prohibited from 1 May -1 September, with beam trawl.Rapa whelk fishing is prohibited from 15 July -1 September with all kinds fishing gears.

Implemented between 1998-1999
Rapa whelk fishing is prohibited from 1 May -1 September with beam trawl.Implemented in 1999 Rapa whelk fishing is prohibited from 1 May -31 August with all kinds fishing gears.

Implemented between 2000-2002
Rapa whelk fishing is prohibited from 1 May -31 August with all kinds fishing gears Rapa whelk fishing by diving is possible between 1 May and 15 July, except in our territorial waters between the Bulgarian border and Samsun Çayağzı Cape and the territorial waters between Anadolu Karaburun and Rumeli Karaburun.

Implemented between 2002-2004
Rapa whelk fishing is prohibited from 1 May -31 August with beam trawl.Implemented between 2004-2016 Rapa whelk fishing is prohibited from 15 April -31 August with beam trawl.
Implemented between 2016-2022 in the study.Within the scope of the study, 80 fishers engaged in Rapa whelk fishing activities in Samsun were interviewed and it was ensured that the fishers used either single or twin beam trawl during a fishing season.58 of the interviewed fishers used twin beam trawl and 22 of them used single beam trawl throughout the season.A survey was conducted with the fishers at the end of the season and the data obtained were analysed to determine the socio-economic effects of the use of twin beam trawl.

Results
Annual landing in Rapa whelk fishing is around 7-10 thousand tons.Forty-five percent of this catch takes place in the Western Black Sea while the rest in the Eastern Black Sea.Approximately 85% of the total landing is caught with beam trawl.Fishing vessels are fishing for an average of 12 hours per day.The number of fishing days varies between 125-150 days (TURKSTAT 2022; Dağtekin et al. 2022).In the assessment made by Dağtekin et al. 2022, the annual income generated from the Rapa whelk sector is per boat $16,767.Fishers send their catches to the factories through the middlemen.Factories make advance payments to fishers.Therefore, they are not very effective in determining the price level in the market.Fishers are affiliated with SÜRKOOP central organization.Another association has been established in recent years.However, the association is not yet effective.
During the periods when the factory does not purchase, fishing stops because there is no demand in the domestic market.Since the international demand for animal food has increased after Covid 19, there has been no problem in demand recently.

Name of the Regulation Description of the regulation Implementation Period
Other Rapa whelk fishing can be done between 1 April -15 July and31 August -30 September between 06.00 -20.00 hours, andbetween 1 October 1986 -31 March 1987 between 07.00 -19.00 hours.

Implemented between 1986-1987
Rapa whelk fishing can be done between 07.00 -17.00 hours in fishing seasons Implemented between 1988-1995 "Rapa whelk fishing license" is obligatory for fishing vessels using the diving method and/or beam trawl during the fishing period.

Implemented between 1999-2004
Rapa whelk fishing must be done between sunrise and sunset.

Implemented between 2004-2022
If there are davits on fishing vessels during the close season, their direction must be towards the inside of the vessel.

Implemented between 2012-2022
Rapa whelk fishing can be done between 05.00 -20.00 hours in fishing seasons.
Implemented between 2016-2022 Fishing of off-target species is prohibited in Rapa whelk fishing with beam trawl.

Evaluation of Management Measures
In this section, the opinions of the stakeholders participating in the workshop on various management measures were discussed.Table 2 summarizes the participants' perspectives on management measures, both on a stakeholder group basis and in general.

Spatial Regulations
Spatial regulation is a management measure that determines how many meters offshore the Rapa whelk fishers should fish at least.

Time Regulations
Under current conditions.fishers cannot fish Rapa whelk with the beam trawler.which is a bottom rubbing tool.between April 15 and August 31.This restriction period is the same as the time restrictions applied to other fishing gear such as trawls and purse seines.There is no time restriction in Rapa whelk fishing by divers.All of the fisheries management officials who attended the workshop stated that this arrangement was appropriate.Fisheries management stakeholders think that it is appropriate to ban Rapa whelk fishing with beam trawl.both because of the protection of the marine habitat and the prohibition of other fishing gear on these dates.The majority of the divers.researchers.and fisheries inspectors who participated in the workshop thought that the time limitation was appropriate.Some researchers and fisheries inspectors think that this restriction period can be rearranged by taking into account the results of scientific research on the reproductive periods of Rapa whelk and other species.Half of the fishers who fish for other species and representatives of non-governmental organizations think that the measure is appropriate.while the other half argue that a new regulation would be beneficial.Some NGO representatives stated that it would be more appropriate for the Rapa whelk fishing restrictions to start on 1 May instead of 15 April in areas that are not breeding grounds for turbot.
Likewise.some of the fishers fishing for other species have also considered it appropriate to end the fishing season in May.June.or July.All of the Rapa whelk fishers and middlemen participating in the workshop.and a significant part of the factory owners.stated that the current time is not appropriate and should be changed.Some of the Rapa whelk fishers demanded that the 1 June -15 July period and some 15 May -15 July periods be open to Rapa whelk fishing with beam trawl.Middlemen argued that the restriction period should be between 1 July and 15 September.and factory owners between 15 July and 31 August.It should be noted that the opinions of the stakeholders.who thought that the current time limitations were not appropriate.were largely influenced by economic concerns.

Discard Related Regulations
Rapa whelk fishing is a type of fishing that can be done with special permission and a single species is targeted.For this reason.it is not legally possible to land and commercialize other non-target species caught in Rapa whelk fishing with beam trawl.The appropriateness of this management measure was evaluated by the stakeholders in the workshop.
When the satisfaction levels of the stakeholders regarding all the current legal regulations discussed in the workshop were examined.it was seen that this management measure had the least satisfaction rate.It was determined that fisheries management officials.fisheries inspectors.NGO representatives.and divers found the current management measure appropriate.However.some divers argued that discards should be landed and commercialized since they have an economic value.The rest of the stakeholders also agreed on the idea of landing and commercialization of discards for some other reasons.Researchers think that knowing the rate and diversity of discards is important for fisheries management.For this reason.some researchers stated that discards should be landed and recorded by following appropriate procedures.In addition.it has been suggested to identify some specific landing points for Rapa whelk fishers.thus making it easier to control the landing of discards.

Fishing Effort
Fishing effort is a measure of fishing intensity and represents time spent searching for fish.Keeping the fishing effort under control is one of the important management tools in ensuring the sustainability of fish stocks and preventing overfishing.Today.there are various measures to control the fishing effort in Rapa whelk fishing.The Rapa whelk fishing ban applied between 20:00 and 05:00 and the prohibition of keeping and using more than one beam trawl on the boats are among these measures.There is no consensus on this issue among the stakeholders participating in the workshop.Fisheries management officials.fishers fishing for other species.and the majority of researchers stated that the current measures are appropriate.They consider current measures to limit fishing efforts significantly.In addition.some researchers have suggested investigating the economic and ecological effects of the use of twin beam trawl.Some of the fishers fishing for other species stated that time restrictions should be removed and the use of twin beam trawl should be legal.While the fisheries inspectors found the existing regulations to be normal.some of the factory owners and NGO representatives stated that the regulations were appropriate and some were not.This disagreement among NGO representatives also exists among Rapa whelk fishers and is due to regional differences.While most of the fishers in the Western Black Sea -Samsun Region demand that the use of twin beam trawl is legal.the fishers in the Eastern Black Sea region do not have such a request.The findings show that divers.middlemen.and Rapa whelk fishers think that the current fishing effort-related regulations are not appropriate and should be changed.These stakeholders stated that it is necessary to have and use twin beam trawl on fishing boats.In addition.some Rapa whelk fishers stated that the fishing ban at night should be removed since the amount of fishable Rapa whelk is higher at night.In general.terms.while managers and researchers prioritize keeping the fishing pressure under control.the stakeholders who have commercial relations with the sector think that the regulations that restrict the fishing effort should be relaxed.

Fishing Gear
The technical characteristics of the fishing gear used in Rapa whelk fishing are very important determining factors in terms of catch amount.discard rate.and its effects on the habitat.For this reason.beam trawl gear used in Rapa whelk fishing has been standardized by legislation.According to this legislation.beam trawls to be used in fishing should have a maximum mouth width of 4 meters.a maximum mouth depth of 40 cm. a maximum bag length of 1.5 meters.and a mesh size of 72 mm.While some of the Rapa whelk fishers.NGO representatives.and middlemen participated in the workshop and found the current legislation appropriate.others stated that various changes were necessary.For example.some fishers stated that the maximum bag length could be 2 meters.On the other hand.middlemen argued that the mesh size should be 60 mm instead of 72 mm in the Eastern Black Sea Region.The reason for this recommendation is that the size of Rapa whelk in the Eastern Black Sea Region is smaller than those in the western regions.Fisheries management officials.divers.fishers of other species.fisheries inspectors.and the majority of factory owners who attended the workshop stated that the current legislation was appropriate.On the other hand.researchers stated that the current legislation is appropriate.but still.new beam trawl designs that will reduce the destruction in the benthic area will be beneficial to the environment.They also emphasized that the effects of the current fishing gear on the rate of discard catch should be determined by landing the discards.

Minimum Fishing Length
One of the tools used in fisheries management to ensure the sustainability of the stocks is the minimum fishing length measure.In this legislation.reproductive maturity is determined by analyzing the life cycle of the fish and it is ensured that the fish are not caught before this period.Although this rule is applied in many fish species caught in the Black Sea.
there is no such limitation in Rapa whelk fishing.The opinions of the stakeholders participating in the workshop on this issue were determined through surveys.The results of the analysis show that the majority of the stakeholder groups think that not implementing such a limitation in Rapa whelk fishing is appropriate.Only NGO representatives stated that the current regulation is insufficient and a minimum fishing length of 3 cm in the Eastern Black Sea and 5 cm in the Western Black Sea can be introduced.While some fishers who are fishing for other species suggest the implementation of regional restrictions.some divers and middlemen reported that a minimum fishing length of 3.5 cm should be introduced.Some fisheries management officials and fisheries inspectors consider that a minimum fishing length measure has been indirectly introduced by the implementation of the 72 mm mesh size rule in fishing gear nets.However.some researchers state that the mesh of the nets becomes clogged and the selectivity decreases when the beam trawl is used for a long time during fishing operations.For this reason.detailed scientific studies on the subject are needed.

Participation
To ensure the control and sustainability of Rapa whelk fishing.the fishers of this species must get permission from the relevant authorities.There is no boat number limitation in Rapa whelk fishing.as is practiced in some species.All fishers who meet the requirements can fish Rapa whelk with beam trawl.The use of this fishing gear is only possible for Rapa whelk fishing in the Black Sea Region.It is forbidden to carry harpoons on fishing vessels engaged in Rapa whelk fishing (scuba diving).In addition.if the vessels authorized for fishing by diving carry boom poles.winches.wire ropes.and davits on board during the period when beam trawling is prohibited.their fishing permits are revoked.In general.most of the stakeholders participating in the workshop stated that the current management measures are appropriate and should continue as such.but there are also some opinions and suggestions to the contrary.For example.some Rapa whelk fishers have suggested that boats be allowed once every two years for Rapa whelk fishing.They also suggested that fishers should make a decision at the beginning of the season and choose to fish Rapa whelk or other species.In parallel with this.some researchers and NGO representatives stated that they found it appropriate to limit the number of fishing boats.

Fishing Capacity
Reducing the fishing capacity is an important measure in terms of reducing the fishing pressure on fish stocks and increasing the technical and economic efficiency of fishers.In Türkiye. the entry of new vessels to the fishing fleet was stopped in 2002.Thus. it was desired to control the fishing capacity.However. the increase in the engine power and technological equipment of the existing boats caused the fishing capacity to increase even though the number of boats did not change.For this reason.the government has introduced a license purchase program to reduce the number of boats.Thus. the licenses of 1264 ships were canceled and the ships were removed from the fleet.This program has led to some reduction in fishing pressure in Rapa whelk fishing as in other species.This issue was also put on the agenda at the stakeholder meeting and the opinions of the stakeholders on the subject were determined through a survey.The results of the analysis showed that the measures for reducing the fishing capacity were the only issue on which all stakeholders agreed during the workshop.Stakeholders stated that the current policy is beneficial and should be continued.In addition.some researchers and some Rapa whelk fishers stated that fishing capacity should be reduced by limiting Rapa whelk fishing boats.Researchers emphasized that the scope of these restrictions should be narrowed or expanded by considering the total amount of catch and the economic situation of fishers.

Quota
One of the most used methods in fisheries management to control fishing pressure on any important species is quota enforcement.There is no quota measure in Rapa whelk fishing in the Black Sea.However.some stakeholders raise the necessity of quota implementation.Divers and other species of fishers stated that a quota should be introduced in Rapa whelk fishing with beam trawl.Some divers stated that a daily quota of 1 tonne per boat could be applied.Some fisheries inspectors and researchers also emphasized that it is important to determine the stock and total amount of Rapa whelk that can be caught for sustainable Rapa whelk fishing.This method is also in line with the opinions of the NGO representatives who argue that regional quotas should be determined and implemented.On the other hand.some of the fishers stated that a daily quota of 600 kg would be appropriate if a 45-day period was open to fish Rapa whelk with beam trawl during the summer season.which is the closed season.Lastly.factory owners stated that they are against any quota implementation since Rapa whelk is an invasive species.

Other Management Measures
In addition to the above-mentioned suggestions.some stakeholders made different recommendations regarding the management of Rapa whelk fisheries.Fisheries management officials stated that Rapa whelk beam trawlers can be included in the ship monitoring system.They also drew attention to the importance of diversifying marketing channels to avoid the low price problem.which was also mentioned by divers.Researchers also stated that the added value of the product should be increased by conducting value chain analyses with a market-oriented approach.Thus.they suggested that factories that generate more income from the product could offer higher prices to fishers.Researchers.controllers.middlemen.and other species fishers stated that they found the current transport and origin document system useful and should continue.

The Use of Single and Twin Beam Trawl
The use of twin beam trawl is frequently demanded by some Rapa whelk fishers in Türkiye.The study determined the differences between the use of twin beam trawl and single beam trawl.Research findings reveal that the average Rapa whelk catch amount with twin beam trawl is 21.4% higher than the fishers using single beam trawl.Similarly.the income of fishers using twin beam trawl from the sale of Rapa whelk is 27.3% higher than that of fishers using single beam trawl (Table 3).These findings also reveal that fishers using twin beam trawl market their products at higher prices.The difference between the average total Rapa whelk incomes was statistically significant (p<0.01)while the difference between the average total Rapa whelk catches of the groups was not.
When the ratio of Rapa whelk income to total fishing income is examined.it has been determined that Rapa whelk has a 4% higher share in the incomes of fishers using twin beam trawl.This finding indicates that fishers using single beam trawl tend to fish different species more than fishers using twin beam trawl.The difference between the groups was not statistically significant.The use of single or twin beam trawl affects the amount of catch and fishers' income as well as fishing costs.Since boats with twin beam trawl can catch more Rapa whelk in one operation.they can save on labor costs and fuel costs.Research findings show that the labor and fuel costs per 1 kg of Rapa whelk for fishers using single beam trawls are 50% higher than those of fishers using twin beam trawls (Table 3).However. the difference between the groups was not statistically significant.

Discussion
It is seen that the problems in the Rapa whelk sector do not differ much from the past to the present (Janssen et al. 2014).However.quota implementation is a management measure demanded by sector stakeholders for a long time.The legal framework of the quota should be well designed (Hatcher 2022).Because it is stated that the fishing pressure on the Rapa whelk stocks in the Black Sea should not be increased (GFCM 2021).It is stated that the current legal mesh size of the beam trawl net does not catch small individuals (L 50 :4.7 cm) (Dağtekin et al. 2021b).Fishers in Turkey generally think that riparian countries catch more Rapa whelk.The minimum catch size of Rapa whelk is 5 cm in Romania (GFCM 2019).It is understood that this assessment is also not valid.It is an important problem that the dates of the closed season for Rapa whelk fishing in the Black Sea basin are different in each country.In the study conducted by Erik et al. (2020).it was stated that the meat yield was low especially in August.It is seen that the productivity of the fishers' fishing during these periods will be lower.
The differences between the use of single and twin beam trawl which is frequently demanded by some fishers were also tested in the study.Research findings reveal that the average Rapa whelk catch amount.income from the sale of Rapa whelk.and the share of income from Rapa whelk in total income were higher in the fishers using twin beam trawl while the average labour cost and the average fuel cost were higher in the fishers using single beam trawl.These findings reveal that the use of twin beam trawl causes a decrease in carbon emissions from fossil fuel consumption for 1 unit of Rapa whelk.However.high fishing capacity and reduced fishing costs may cause an increase in fishing pressure (Dağtekin et al. 2022).How this scenario will affect the sustainability of Rapa whelk fishing is one of the issues that need to be investigated.In addition.increased fishing pressure and use of beam trawl will increase its impact on the habitat and other species.Therefore.the effects of twin beam trawl use on Rapa whelk.other species.and habitat should be investigated in detail.Taking different management measures to reduce fishing pressure is also very important for sustainable fisheries.
Boat owners' request to fix the number of Rapa whelk fishing boats is acceptable.In line with this request.at the GFCM 2022 WGBS meeting.the results of the stock analysis stated that the fishing effort should not be increased.It is understood that there is a decrease in stocks during the surveys conducted within the scope of the GFCMsupported BS4F project (Dağtekin et al. 2021b).Therefore.it is imperative to avoid practices that increase effort.Another issue that stakeholders should consider is the damage caused by beam trawling to the benthic habitat (Kaiser and Spencer 1996; Fig. 2).Therefore.it is necessary to design more eco-friendly beam trawl prototypes and adapt Rapa whelk fishing.

Conclusions
Since public policies in Rapa whelk fisheries management are determined directly by the management authority.there are deficiencies in research that integrates the knowledge of stakeholders and scientists (Pita et al. 2010).Today. it is seen that there are significant deficiencies in fisheries management worldwide.The causes and possible solutions to these problems often lead to political debate.Is the solution more and better science or more and better politics?Is there a need to improve the first.the second or both?Or is something else missing?These question marks are always there (Mackinson et al. 2011).Management measures should be developed based on the answer to these questions.
The Rapa whelk stakeholder meeting revealed that there is a need for a holistic approach to Rapa fisheries management.However.instead.it has been seen that the focus is on management measures as it is a simpler way.Currently.processing plants only collect the product and export it in the cold chain after extracting the meat.Since Rapa whelk is not usually sold in the domestic market in Türkiye.all production is exported.Cooperatives do not have any influence on the Rapa whelk market.There is no effort to increase the added value of the product.Therefore.the main goal of such associations and fishers is to change the legislation and try to fish more Rapa whelk.Only a certain level of fishing should be done to ensure the sustainability of the resource.On the other hand.fishers argue that Rapa is an invasive species and should be fished until it disappears from the ecosystem.However.as in many seas in the world.it is known that invasive species adapt to the ecosystem over time and take place in the food chain.For this reason.it is important to keep the use of beam trawling under control.which damages the benthic habitat.especially during intensive fishing periods.Industry stakeholders should be aware of this mechanism.Some fishers recommend the use of twin beam trawl for Rapa whelk fishing.Fishers state that less fuel will be spent in this way.Economic indicators also show the twin beam trawl attractive.In such a case. it is useful to examine to what extent the benthic habitat will be affected.The use of single beam trawl and twin beam trawl can be compared ecologically and economically.If the use of twin beam trawl is appropriate.the effort should be reduced.In such a scenario.a limitation such as the half-day operation of each boat may be introduced.Another important issue is that the fishers in the Eastern Black Sea do not want twin beam trawl.Since the coastal areas are very narrow.fishing with twin beam trawl is not suitable in these regions.Therefore.such an arrangement can only be regional.
It is also very important to carry out studies that will increase the economic value of Rapa whelk.Considering that the shell weight is at the level of 50% (Erik et al. 2020).various alternatives should be evaluated such as ornaments.octopus fishing.and chitosan production.In addition.while the meat weight is 50% of the total weight.the edible meat rate is 15-20% (Erik et al. 2020).Therefore.it would be beneficial for the sector to make an effort to use the non-edible and discarded parts in the feed industry.
While taking management measures.it is necessary to evaluate the Black Sea basin as a whole.There is a need for the Black Sea riparian countries to come together and implement the same legislation.It is not possible to say that countries are currently cooperating in both the fishing time and the fishing gear regulations.This situation strengthens the persuasion of industry stakeholders about a management measure not implemented in other countries.This situation poses a problem in fisheries management.For this reason.a joint management plan in the Black Sea should be determined and implemented.

Fig. 2
Fig. 2 Effect of beam trawl on benthic habitat (original)

Table 1
Changes in regulations related to R.venosa until now

Table 1
(continued) Currently.fishers are restricted by regulations from fishing for Rapa whelk at a distance of fewer than 500 meters from shore.Due to the different continental shelves in the Western Black Sea and the Eastern Black Sea. the depths at a distance of 500 meters from the land differ.While the depth increases more rapidly.especially in the Eastern Black Sea Region. it is known that there is a lower acceleration in the Western Black Sea regions.This situation leads to the questioning of the 500 meters rule.which is currently being implemented.In the workshop.the opinions and suggestions of the participants about this measure were determined.According to the results of the survey conducted with the stakeholders.while the majority of the participants argued that the 500 meters distance rule should be rearranged by taking into account the depth and distance.some stakeholders stated that the current management measure is more appropriate for some reasons including applicability.All divers participating in the survey.representatives of nongovernmental organizations.brokers.fishers fishing for other species.and factory owners agreed on the idea of introducing a new distance rule by considering depth.It is seen that 75% of the researchers participating in the survey agree with this idea.When the answers of the fishers engaged in Rapa whelk fishing were examined.it was seen that the fishers fishing in the Western Black Sea Region were satisfied with the current regulation.but the Rapa whelk fishers in the Eastern Black Sea Region argued that new regulation should be introduced by considering the depth and distance.This situation is related to the fact that the fishers in the Eastern Black Sea have to fish for Rapa whelk in more disadvantageous conditions in deeper waters.The majority of the fisheries management officials participating in the workshop stated that the current 500 meters rule is appropriate in terms of protecting the marine habitat and preventing conflict with other fishing activities operating in coastal areas.While half of the fisheries inspectors responsible for the implementation of the management measures taken defended the existing regulation.the other half favoured a new regulation to

Table 2
The score of stakeholders according to fisheries management measures be introduced by considering the depth.Fisheries inspectors.who found the current regulation appropriate.stated that a new distance rule to be introduced according to the depth would cause different distances to be applied in each region and therefore controllability would decrease.

Table 3
Differences between use of single and twin beam trawl