Recovery Signals of Rhodoliths Beds since Bottom Trawling Ban in the SCI Menorca Channel (Western Mediterranean)

One of the objectives of the LIFE IP INTEMARES project is to assess the impact of bottom trawling on the vulnerable benthic habitats of the circalittoral bottoms of the Menorca Channel (western Mediterranean), designated a Site of Community Importance (SCI) within the Natura 2000 network. The present study compares the epibenthic communities of four areas, subjected to different bottom trawl fishing intensity levels. The assignment of fishing effort levels was based on the fishing effort distribution in the area calculated from Vessel Monitoring System (VMS) data and the existence of two Fishing Protected Zones in the Menorca Channel. Biological samples were collected from 39 beam trawl stations, sampled during a scientific survey on April 2019. We compare the diversity, composition, and density of the epibenthic flora and fauna, together with the rhodoliths coverage and the morphology of the main species of rhodoliths of four areas subjected to different levels of bottom trawl fishing effort, including one that has never been impacted by trawling. Our results have shown negative impacts of bottom trawling on rhodoliths beds and the first signals of their recovery in areas recently closed to this fishery, which indicate that this is an effective measure for the conservation of this habitat of special interest and must be included in the management plan required to declare the Menorca Channel as a Special Area of Conservation.

Mathematical model for determining the roll angle of a fishing vessel when purse seine sampling

Лов рыбы с применением кошельковых неводов является наиболее распространенным в мире после тралового лова. Процессы кошелькования невода, выборки улова могут существенно влиять на остойчивость рыболовного судна (сейнера). В данной работе рассматривается влияние на угол крена силы, действующие со стороны орудия лова. Приведен алгоритм расчета, учитывающий координаты точки приложения силы натяжения троса, идущего к орудию лова, углы наклона троса, величину силы. Составлены расчетные зависимости для процессов крена, получены выражения для угла наклона корпуса судна. Приведены примеры расчетов. В частности, рассмотрено изменение угла крена от тягового усилия, высоты подъема канифас-блока для промыслового судна. Проведенные расчеты свидетельствуют о достаточной для инженерных расчетов точности и возможности использовать приведенный алгоритм при оценочных расчетах на различных стадиях проектирования. Важно учитывать возможность одновременного наложения ветровых нагрузок, действия волн на корпус судна. В этих случаях крен и дифферент будут возрастать. Поэтому спецификой промысловых судов является необходимость учета поведения судна при проведении промысловых операций. Fishing with the use of purse seines is the most common in the world after trawl fishing. The processes of pursing and seine sampling can significantly affect the stability of a fishing vessel (seiner). In this paper, the influence of forces acting from the fishing gear on the roll angle is considered. The calculation algorithm is given, taking into account the coordinates of the point of application of the tension force of the cable going to the fishing gear, the angles of inclination of the cable, the magnitude of the force. Calculated dependences for roll processes are compiled, expressions for the angle of inclination of the vessel's hull are obtained. Examples of calculations are given. In particular, the change in the roll angle from the traction force, the lifting height of the snatch–block for a fishing vessel is considered. The calculations carried out indicate sufficient accuracy for engineering calculations and the possibility of using the above algorithm for evaluation calculations at various stages of design. It is important to take into account the possibility of simultaneous imposition of wind loads, the action of waves on the hull of the vessel. In these cases, the roll and trim will increase. Therefore, the specifics of fishing vessels is the need to take into account the behavior of the vessel during fishing operations.

Length–weight relationship of Charybdis callianassa Herbst, 1789 (Decapoda: Brachyura) in relation to sex and carapace length along the Mumbai coastal water, India

Background The present study was performed to determine carapace length–body weight relationship of Charybdis callianassa. In fisheries biology, length–weight relationships are important as they allow for the calculation, by creating a mathematical equation between the two, of the total weight of the fish in a particular group in fish. Such information is helpful for fishery scientists to research the dynamics of development and populations and for public agencies that can maintain and preserve these resources sustainably. Results A study on the carapace length–body weight relationship of Charybdis callianassa (Herbst, 1789) was made on the northwest coast of India for the first time. The study was based on experimental trawl fishing conducted fortnightly from August 2019 to March 2020. A total of 479 specimens, including 262 males and 217 females from fishing trawler, were examined for their carapace length and total weight. The carapace length ranged from 2.69 to 3.54 cm, and the total weight from 5.26 to 7.36 g. This analysis revealed that the crabs exhibited negative allometric development, as shown by average exponents 'b' = 2.71 for pooled data with high coefficient (r) = 0.91 and r2 = 0.83. Conclusions The carapace length–body weight relationship of Charybdis callianassa in relation to sex and carapace was studied in the Mumbai coastal water, India. We found major differences in the average “r2” values of species reported for males (0.89), females (0.79) and pooled data (0.83). Such kind of study is essential for fisheries biology to comprehend the differences in circumstances in small and large specimens that vary with environmental conditions and seasons.

Fishing trawl modernization methods under ship thrust deficiency during voyage

The article considers the problems of compatibility between the hydrodynamic resistance of the trawl and the actual trawler's thrust, which have lost the ability to provide the necessary traction force due to the increase in the resistance of the ship's hull and wear of the engine-propulsion system. The area of resistance of the trawl system is proposed to be reduced by reducing the linear dimensions of the layers of the trawl part, as well as by replacing some layers of the trawl with a smaller mesh by those with larger meshes. It is noted that during fishing vessel masters often make an intuitive decision to replace trawls with those of less powerful vessels. Methods of reducing the area of trawl resistance are considered, which will lead to a decrease in its hydrodynamic resistance of the trawl fishing system. Numerical examples of the considered technique are given. The trawl plate P-K-120/1120, full-scale and modernized parts of the trawl are illustrated. The results of the trawl part modernization are presented, and the formula for calculating the fictitious trawl area is presented. The method of modernization of the trawl due to the increase in the size of the trawl in some parts of the trawl is analyzed, the average weighted step of the mesh in the full-scale trawl is calculated. The developed methodology should allow solving the problem of trawl modernization promptly, in the conditions of the fishing deck, by the forces of the ship’s crew. The proposed methods for the modernization of a fishing trawl will allow avoiding large costs for the repair of the main engine of a fishing vessel operating a trawl that does not correspond to the technical condition of the trawler, or to reduce the underfishing with a smaller trawl.

Analysis of The Potential Banana Prawn (Penaeus merguiensis) in The Northern Waters of Rembang Regency

This study aims to describe the characteristics of mini bottom trawl fishing gear and fishing season, as well as to estimate the stock density and sustainable potential of banana prawn (Penaeus merguiensis), in Rembang Regency. This study was conducted from September to October 2020, in the Northern Waters of Rembang Regency, with an area of ​​1409.7 km², using both primary and secondary data. Primary data was collected directly from observations, measurements, and interviews with fishermen, while secondary data, including data on the number and types of fishing gear, as well as production and production values, was obtained through a literature review. The results of the study found that banana prawn in the northern waters of Rembang Regency was caught using two types of fishing gear, and these are sotok/mini bottom trawls and trammel nets. The total length of mini bottom trawl in this study are 15.77 m, 16.5 m, 20.44 m, and 25.2 m. The fishing season for banana prawn is from June to September The average stock density value is 16.22 kg/km² (range 4.37 to 41.14 kg/km²), the Cmsy value is 2.625 kg, the Emsy value is 4.172 trips and the average utilization rate is 44% (range 23 to 82%). Keywords: Rembang, banana prawn, stock density, and MSY.

Estimation of Maneuverability of Trawl Fishing Vessel Using an Analytical Method

Most fishing vessels are less than 100 m in length between the perpendiculars, for which adherence to the International Maritime Organization maneuverability standards are not mandatory. In the design stage of fishing vessels, maneuverability is estimated using empirical formulas—mainly analytical methods—rather than costly and time-consuming model tests. However, the empirical formula is developed through the process of regression analysis on the model test results from merchant ships’ hull form and applying the same to the fishing vessels’ hull form may result in an estimation error due to the differences in the vessels’ characteristics—e.g., L/B, B/d and Cb·B/L—. In a previous study, the authors of this paper derived a modified empirical formula by adding the hull form parameters of trawl fishing vessels to the existing empirical formula based on those of merchant ships. This study analyzes the validity of the modified empirical formula in depth by applying it to a newly-built training vessel that has the hull form of a trawl fishing vessel. As a result of the study, the estimation results were improved by including the parameters of the hull form of trawl fishing vessels in the empirical formula developed for merchant ships.

Comparison of Nutrition Values of Discarded Fish By Bottom Trawl Fishing in the Mersin Bay

In the present study, proximate composition and meat yield of discarded fish Tub gurnard (Chelidonichthys lucerna Linnaeus, 1758), brown comber(Serranus hepatus Linnaeus, 1758) and Scaldfish (Arnoglosus laterna Walbaum, 1792) caught in Mersin Bay (Northeastern Mediterranean) by bottom trawlers were investigated. The highest protein values and the lowest total lipid and ash values were recorded during spring in three species (P<0.05). Meat yield was found to be different significantly among spring and autumn samples (P<0.05). Mean meat yield of tub gurnard, brown comber and scaldfish were 50.94%, 53.85% and 64.56%, respectively. Results of study show that although these species are considered to be discarded, they can be considered as food or additive for various living groups due to their high nutritional quality, thus they can contribute significantly to the food requirement and economy of the country. Thus, both the ecological balance in the marine environment will be protected and economic losses will be prevented.

Length-Weight Relationship of 60 Fish Species From the Eastern Mediterranean Sea, Egypt (GFCM-GSA 26)

Length-weight relationships (LWRs) are described for 60 important pelagic and demersal fish species caught during fishing surveys using trawl fishing gear in the Eastern Mediterranean, Egypt (General Fisheries Commission for the Mediterranean GFCM-GSA 26), and the data collected from the commercial catch during the period from July 2017 to December 2018. Linear regression using natural logarithmic transformation data was performed to calculate the a and b coefficients of LWR for 60 fish populations covering 23 families, 43 genera, and 60 species inhabiting GSA 26. The samples size, minimum and maximum lengths and weights with their mean and SD, LWR constants, ± 95% confidence interval (CI) of b, r2, and the type of growth were calculated and summarized. This study reports the first LWR estimates for 35 species in the Egyptian waters of the Mediterranean Sea.

Prohibition of Bottom Trawling on Extended Continental Shelves: Creeping Jurisdiction or Enforcement of Sovereign Rights?

This article discusses whether the regime of the continental shelf includes a right to conserve living natural resources and whether a unilateral establishment of a ban on bottom trawl fishing is possible on the high seas superjacent the extended continental shelf (ECS). Based on Article 77 and Part XII of the United Nations Convention on the Law of the Sea, coastal States can impose reasonable conservation measures to protect sedentary species from harmful fishing practices. The article also explores how the competing rights of coastal and flag States, as well rights of coastal States with overlapping ECS entitlements, should be balanced in case of the imposition of unilateral conservation measures.