In 2014, the greatest share in the total catch of R. venosa (1953 t) was held by the
fleet segment 12–18 m, with a percentage of 45%, while catches taken by manual
harvesting with divers represented about 20% of the total catch.
With reference to selectivity, the size of the R. venosa specimens retained by the
bag of the beam trawl, during fishing operations, varied between 5.5–11.5 cm,
which demonstrates that the mesh size of 5.5 cm ensures a good selectivity.
The rapa whelk catches achieved by vessels engaged in fishing activities along
the Romanian coast are contracted by processing factories/plants and by other
companies in the country and abroad, which capitalize it in the market in various
forms (fresh, frozen, canned). Local restaurants have also started to include
R. venosa in their menus.
23.4 Conclusions
Changes in the fish fauna composition of the Black Sea have primarily involved
alterations in the number of individuals in specific populations and, for many
species, fish populations have declined so sharply that they have lost their importance for commercial fishing. These changes reflected in the overall catches
recorded, which dropped sharply during 1990s–2000s. However, starting with
2009, Romanian Black Sea fishery catches have recorded an increasing trend.
Yet, this is not the consequence of a massive restoration of fish stocks or an increase
of fishing effort, but the result of shifting the target species. The invasive gastropod
R. venosa has raised the interest of economic operators due to its low exploitation
costs compared to other valuable species (turbot, for instance).
During 2009–2012, rapa whelk fishing was made only by hand, by divers, being
the only harvesting technique allowed by legislation. Starting with 2013, beam
trawls were legalized and started to be used. Consequently, catches have increased
from 1 year to the other, from approximately 1.7 t (2009) up to 1338 t (2013). Once
the beam trawl use has become legal, many commercial companies in the field have
shifted their business towards purchasing or manufacturing this type of gear,
corresponding to their vessel capacity. As such, the number of vessels equipped
with this type of gear has increased yearly, and many of them have two beam trawls
towed simultaneously.
From the selectivity point of view, the gear used for rapa whelk fishing (beam
trawl) does not retain immature specimens of R. venosa and no juvenile fish
belonging to certain demersal fish species (gobies, red mullet, whiting). Rarely in
catches of rapa whelk may appear some juveniles of turbot, flounder and sole,
however, after emptying the bag they are released in to the sea. Yet, there is some
concern on the potential effects of beam trawl on the seabed (Zengin 2006), which
should be investigated in the future (Danilov et al. 2015).
Also, as a consequence of exploitation, the drop of R. venosa populations was
acknowledged, which requires future research meant to determine the actual stock
size and total allowable catch (TAC), aiming at underpinning the rapa whelk
23 New Equipment and Technologies Used for Rapa Whelk Harvesting at the. . .
403
fleet segment 12–18 m, with a percentage of 45%, while catches taken by manual
harvesting with divers represented about 20% of the total catch.
With reference to selectivity, the size of the R. venosa specimens retained by the
bag of the beam trawl, during fishing operations, varied between 5.5–11.5 cm,
which demonstrates that the mesh size of 5.5 cm ensures a good selectivity.
The rapa whelk catches achieved by vessels engaged in fishing activities along
the Romanian coast are contracted by processing factories/plants and by other
companies in the country and abroad, which capitalize it in the market in various
forms (fresh, frozen, canned). Local restaurants have also started to include
R. venosa in their menus.
23.4 Conclusions
Changes in the fish fauna composition of the Black Sea have primarily involved
alterations in the number of individuals in specific populations and, for many
species, fish populations have declined so sharply that they have lost their importance for commercial fishing. These changes reflected in the overall catches
recorded, which dropped sharply during 1990s–2000s. However, starting with
2009, Romanian Black Sea fishery catches have recorded an increasing trend.
Yet, this is not the consequence of a massive restoration of fish stocks or an increase
of fishing effort, but the result of shifting the target species. The invasive gastropod
R. venosa has raised the interest of economic operators due to its low exploitation
costs compared to other valuable species (turbot, for instance).
During 2009–2012, rapa whelk fishing was made only by hand, by divers, being
the only harvesting technique allowed by legislation. Starting with 2013, beam
trawls were legalized and started to be used. Consequently, catches have increased
from 1 year to the other, from approximately 1.7 t (2009) up to 1338 t (2013). Once
the beam trawl use has become legal, many commercial companies in the field have
shifted their business towards purchasing or manufacturing this type of gear,
corresponding to their vessel capacity. As such, the number of vessels equipped
with this type of gear has increased yearly, and many of them have two beam trawls
towed simultaneously.
From the selectivity point of view, the gear used for rapa whelk fishing (beam
trawl) does not retain immature specimens of R. venosa and no juvenile fish
belonging to certain demersal fish species (gobies, red mullet, whiting). Rarely in
catches of rapa whelk may appear some juveniles of turbot, flounder and sole,
however, after emptying the bag they are released in to the sea. Yet, there is some
concern on the potential effects of beam trawl on the seabed (Zengin 2006), which
should be investigated in the future (Danilov et al. 2015).
Also, as a consequence of exploitation, the drop of R. venosa populations was
acknowledged, which requires future research meant to determine the actual stock
size and total allowable catch (TAC), aiming at underpinning the rapa whelk
23 New Equipment and Technologies Used for Rapa Whelk Harvesting at the. . .
403