Fisheries characteristics and biology of Indo-Pacific King Mackerel in Tarakan Waters, North Kalimantan

The Indo-Pacific king mackerel (Scomberomorus gutatus) is one of the catches of drift gill nets in the waters of Tarakan, north Kalimantan, and makes an important contribution to fisheries production in the region. In order for its use to be sustainable, it is necessary to make efforts to manage fish resources based on studies of fisheries and their biology. Monthly data for the period January to November 2021 were obtained from tangkahan based on tarakan with the aim of obtaining information and analyzing the dimensions of fishing gear, fishing grounds, catch composition, frequency of fish size, and fishing effort (cpue). Furthermore, fish biology data were analyzed by the analytical method. the results showed that there was a change in the dimensions of the longer fishing gear; the abundance of fish caught by drift gill nets was dominated by indo-pacific king mackerel (Scomberomorus gutatus) (49.3%), dorab wolf-herring (Chirocentrus dorab) (12.8%), fourfinger threadfin (Eleutheronema tetradactylum) (8.5%), silver grunt (Pomadasys argenteus) (4.7%), narrowbar spanish mackerel (Scomberomorus commerson) (4.3%), barramundi (Lates calcarifer) (2.3%), goldstripe sardinella (Sardinella gibbosa) (2.2%), common pike conger (Muraenesox bagio) (2.2%), daggertooth pike conger (Muraenesox cinereus) (1.9%), needleskin queenfish (Scomberoides tol) 1.7%, great barracuda (Sphyraena barracuda) 1.3%, and other fish (11.1%). The distribution of fishing grounds is dominated by grid 6005 by 46.5%, grid 6004 by 7.08%, and grid 5760 by 6.7%. The length at first capture (lc) of mackerel was 38.06 cmfl. The yield per unit effort (cpue) of drift gill nets in Tarakan is an average of 44.3 kg/day.


Introduction
In the utilization and management of fishery resources, we are often faced with how many obstacles and challenges there are and how to utilize these fishery resources.To generate and 2 contribute to the fishing economy.Meanwhile, sustainability must be well maintained for future generations.Challenges will increase when various fish stocks are intensively exploited and fishing pressures are vulnerable to the availability of fish resources.For this reason, the availability of scientific data is very helpful in informing the development of fisheries in each fisheries management area, especially in the Indonesian Fisheries Management Area (IFMA) 716.
The Indo-Pacific king mackerel (Scomberomorus guttatus) is one of the species of the genus Scombridae in Indonesian waters.The plank spreads throughout the coastal areas and islands of Indonesia and migrates closer to the coast than in the narrow margins of the Spanish mackerel (Scomberomorus commerson).These habitats are in waters that are not very clean and have low salinity [1]; [2]; [3]; [4]; [5]; [6]; [7]; [8].
Generally, these fish are caught by drift gill nets by fishermen who are catching fish in Tarakan waters.The production of plank mackerel in the Indonesian Fisheries Management Area (WPP/IFMA) 716 for the period 2005-2020 reached 5,177.3tons, with an annual average of 323.66 tons [9].Based on enumerator data for 2017-2021, mackerel fish production in the Tarakan area is 178.5 tons, or around 3.5% of the total production of IFMA 716.The data shows that the production of IFMA 716 is mostly caught using 10 gross tons (GT) of small vessels with gillnet fishing gear or drift gill nets.The fishermen's catch is then sold to Tangkahan.This is a privately owned landing site integrated with cold storage, workshops, and landing ports.The landing port serves every fishing vessel to unload fish and process the catch before export.Fishermen's landing sites at IFMA 716 are widespread on every coast of small islands, fishermen's Tangkahan, and fishing ports.The Indo-Pacific king mackerel has long been caught by traditional and modern fishermen and is a species that is targeted by fishermen because of its high economic value, both in local marketing and export, especially to Malaysia and Singapore [10].Efforts to catch this fish are getting more intensive, but management is still lacking.The concern is that the continuous exploitation will make the availability of the Indo-Pacific mackerel vulnerable.Therefore, this study was conducted to determine the condition of how much fish has been used, the level of abundance, the value of the length of the first caught, and the distribution of the mackerel fishing area in Tarakan waters to control overexploitation.

Data Collection
Research on Indo-Pacific king mackerel fisheries in Tarakan waters, North Kalimantan, was carried out in Tangkahan Ismail in the period January to November 2021.The results of observations during the study obtained data, namely data on ship specifications, dimensions of fishing gear, number of ships landing the catch, dominant species, the size of the vessel, the size of the length of the fish, operations, and fishing grounds for Indo-Pacific king mackerel.
To support this information, interviews or discussions with the captain and crew were conducted.
Estimation of the abundance of drift gill net catches, number of boat trips obtained from tangkahan and enumerator data, as well as data on the frequency distribution of mackerel for the period January to November 2021.

Data Analysis
CPUE calculation refers [11] using the equation: CPUE = yield catch per fishing effort (tons/trip) Catch = total catch (tons) Effort = total fishing effort (trip)

Specifications and dimensions of drift gill nets
The results of the measurement of the dimensions of the drift gill net fleets found that there were differences in the size of the line length and size of the ships, namely the length of the net is about 500 m, 720 m, 1100 m, and 1500 m in nets ranging from 3-5 meters with different sizes and weights of ships.Generally, the length of the drift gill nets is 1100 m.One example of the drift gill net fleet that is used as a sampling is KM.Cahi, and the main material of the ship is wood.The dimensions of the ship are L = 12 m long, B = 2.2 m wide, and D = 1.5 m deep.Gross tonnage: 11.Dong Feng's main engine is 42 PK, and the crew is as many as 2-3 people.The fishing gear is a floating gill net with a top row of 1100 m (PE 10 mm, 50 mx 22 pis per pis), a 1210 m bottom rigging rope, 1" nylon material (Taiwanese nylon), a total weight of 1467 pieces (@ PB 16 grm), and a net of 2.8 m (Figure 1).Dimensional measurement results.

Fishing ground area
A Tarakan-based drift gill net fleet per trip takes about 2-6 days to fish around the waters of Tarakan and the EEZ border of Indonesia and Malaysia, with a distance of about 5-40 miles (distance is about 1-5 hours) to the fishing ground (Table 2).The results showed that the fishing areas of drift gill nets visited by fishermen were dominated by grid 6005 with as many as 894 tawur or 47%, grid 5270 with as many as 474 tawur or 25%, grid 515 with as many as 214 tawur or 11%, grids 5760 and 6004 with as many as 129 and 136 tawur or 7-7.1%, and grids 5271, 5516, 5758, and 5759 with as much as 1% (Table 1, Figure 2 and Figure 3).

Composition
Catches of drifting gill net as many as 30 species: indo-pacific king mackerel 50.3%, dorab wolfherring 13.0%, fourfinger threadfin 8.6%, javelin grunt 4.8%, narrowbar spanish mackerel 4.4%, giant trevally 2.4%, tardoore 2.2%, daggertooth pike conger 2.3%, needleskin queenfish 1.8%, torpedo scad and pestle 1.4%, great barracuda 2%, Japanese Bigeye 1,20%, and other fish below 1% (Figure 3).Structure of fork length of Indo-Pacific king mackerel (Scomberomorus gutatus) in Indonesian Fisheries Management Area (IFMA) waters: 716 were landed on Tarakan using drift gill net fishing gear ranging from 23 cm to 55.4 cm FL.Where there are 3 modes, namely in the length range of 24.1-24.9cm FL, 25.1-25.9cm FL, and 26.1-26.9cm FL.The highest mode in March is the length range of 25.1-25.9cm FL.The shift in the length of the black mackerel occurred from January to April, while from May to November it was relatively the same (Figure 4).The average length at first caught size (Lc) of mackerel in the Tarakan Sea, Sulawesi, is 38.06 cmFL (Tables and Figures 5)

Discussion
Changes in the dimensions of drift gill nets in the Tarakan area were caused by the increase in the number of days in fishing trips, ship size, ship weight, and increased demand for local communities and for export commodities.This causes the gill net fishermen to drift away to make excessive use.The difference in dimensions between the length of the top rope and the size of the boat is a requirement and an effort for fishermen to get optimal catches and increase their productivity.Mackerel is generally caught with gillnets, with dimensions of the length of the ris line on average ranging from 720-900 and 1000-1500 meters with a net depth of 3-5 meters; even in WPP 711, the length of the upper ris line is up to 2500 m with a net of 10-15 m [12]; [13]; [14]; [15]; [16].
In oceanic waters where the dominant water mass comes from the Pacific Ocean, in the Sulawesi Sea, many economically important pelagic species such as tuna, neritic tuna, and mackerel are caught.Large pelagic fishing areas exist in almost all waters of WPP 716 in the Sulawesi Sea.The fishing grounds for gillnet fishermen with vessel sizes 5-12 GT based in Tarakan cover a fairly large area, from the waters of Nunukan (Karang Unarang) to Sambit Island.In January, the gillnet fishing area was concentrated on grid 6005 with 61 tawur, namely around Maratua Island and grid 6004 with 56 tawur (to the south of Tarakan), and only around Bunyu Island with 20 tawur to the north of Tarakan.From February to August, the distribution of fishing grounds is generally on grids 6005, 6004, 5515, and 5270, even until the transition of the west season (December).The concentration of drift gill net fishing areas in this area is thought to be due to the slightly murky waters and low salinity where mackerel and other mackerel species migrate to depths ranging from 10 to 40 meters [17]; [18]; [19].Stated that mackerel fish are suspected to be roaming along a certain level or degree of salinity [20].This is because fish are very sensitive to changes in salinity of 0.02 per mile.The optimum salinity range for mackerel, according to 34.21-34.60/ 00 [21].
The composition of gillnet catches consists of many types of fish, and the level of biodiversity is still high, at around 30 species or more.The composition of mackerel species is 49.3%, and the average catch of mackerel remains dominant, which is around 2,528 kg per month, machete machete 656 kg per month, pleasure 433 kg per month, arut 263 kg per month, mackerel rod 241 kg per month, and other fish ranging from between 2 and 146 kg per day.The results of Salim's research (2017) show that the composition of the caught fish species and the biodiversity (12 species) of drift gill nets are smaller.Results.The composition of the catch showed two dominant species, namely mackerel and machete.Sustainability in the abundance of this type of fish must be maintained with a pattern of regulation of fishing effort.By knowing the time series, the abundance of biodiversity is maintained.If a change in abundance is identified, it can be said that there has been fishing pressure from the operation of gillnets because it can be seen that fish species are in certain habitats and interact with each other [12].The results of research by [16] showed that only 1% of mackerel caught with gill nets in the South China Sea.The frequency distribution of the length of the mackerel (Scomberomorus gutatus) ranged from 23 cm to 55.4 cmFL, with a length mode of 25.1-24.9cmFL.[22]; [23]; [24]; [25]; [26]; [27]; [28].The mode value shows that the fish caught are dominated by large fish or have mature gonads.The structure of the length of the mackerel was observed every month, indicating that the mode value was almost the same every month.The other size and mode groups are only slightly visible.This is thought to be due to the fishing gear used by fishermen, who almost entirely use gillnets to catch mackerel.It can be seen that the gillnet is a fishing gear that is quite selective for catching fish.The difference in the size of the fish caught in each location is caused by differences in mesh size, size distribution, and fishing areas.The value of the size mode of plank mackerel in the waters of WPPNRI 716 shows the number of adults caught.But there are still a lot of small fish caught.The percentage of small fish caught can be reduced by enlarging the meshes and regulating fishing areas.Fishing areas near the coast (nursery grounds) sometimes cause more small fish to be caught.Plank mackerel also has habitat preferences related to feeding habits, suitability of water conditions, and safety from predators, so fishing activities must also be regulated by considering these things, especially in multispecies fisheries.Size structure varies every month, mode values are in the same range almost the same every month.Size structure varies every month, but mode values are in the same range almost every month.In March, peak mode begins to appear until the end of the year.The presence of three peaks in this mode indicates that there are a number of age groups of fish that have started to enter the waters due to recruitment.The structure of the size of the plank mackerel shows the presence of small fish that began to appear in March.The same mode value every month proves that gillnet has high selectivity.The size structure of fish that has shown recruitment in certain months can be used as a basis for regulating fishing activities.Fishing activities can be regulated by looking at when recruitment begins to enter the waters or enters the nursery grounds and considering the spawning season for fish.The peak of recruitment is presented by the presence of small fish sizes in the size structure; fishing activities can be temporarily closed (close season) or catching can be transferred to other fishing areas with other fish targets.
The average length of the first mackerel caught using a drift gillnet was 38.06 cm FL.This value is greater than that reported by [29] in India, which is 21.1 cm; [30] in the waters of the western Indian Ocean, which is 21.05 cm; [31] in Bangladesh waters, by 40.3 cm; in Riau Islands, by 41.8 cm (2018); and by [32] in Cilacap waters, by 32.7 cm.This difference in value is caused by the use of different mesh sizes and fishing areas.The Lc value must be greater than the Lm value so that the recruitment process can take place properly.Mackerel production fluctuated and showed an increasing trend for the period 2005-2020.The total catch was 5,177.3tons.Mackerel fishing efforts recorded based on enumerator data for 2017-2021 are 178.5 tons, or around 3.5% of WPP 716.From the trend of enumerator data, it seems that the enumerator data fluctuates and tends to increase, but the impact of COVID-19 for the 2020-2022 period affects fishing efforts.This can be seen in 2019 and 2020, when production increased, and in 2021, when it experienced a declining trend of 27.3%.The decrease in production has an impact on the decrease in CPUE value; the average CPUE value in 2017-2021 was 44.3 kg per day, with the highest CPUE value in 2020 at 51.0 kg per day and the lowest CPUE value in 2021 at 36.6 kg per day.The decrease in fishing effort has an impact on the CPUE value of mackerel per day, and it is hoped that in the future, with the decline in COVID 19, the productivity of drift gill nets will recover to utilize the potential of mackerel in Tarakan waters.

Conclusion
Indo-Pacific king mackerel in the waters of Tarakan FMA 716 caught with drift gill nets are generally caught with vessels of < 10 GT, with the length of the upper reef line generally ranging from 1000-1100 m with a depth of 3.8 m.The composition of the catch of mackerel each month dominates the catch of drift gill nets, with an average catch of 44.3 kg per day.This shows that the plank mackerel fishery with floating gill nets can still be utilized with the principles of prudence and sustainable environmental friendliness.

Figure 1 .
Figure 1.Design of drift gill net on a fleet of 11 GT in Tarakan

Figure 2 .
Figure 2. Fishing ground drift gill net for months in 2021

Figure 3 .
Figure 3. Composition of fish species caught by drift gill nets based on Tarakan 2021.

Figure 4 .
Figure 4. Frequency structure of the length of the Indo-Pacific king mackerel in Tarakan IFMA 716 in 2021.

Figure 5 .
Figure 5. Lc value of indo pacific king mackerel in the waters of the Sulawesi Sea IFMA 716 in 2021

Figure 6 . 9 Figure 7 .
Figure 6.Fluctuation of production of Indo-Pacific king mackerel and number of trips by drift gill net landed at Tarakan, 2005-2021

Table 1 .
Number of drif gill net by fishing ground based on Tarakan, 2021 The drifting gillnet fishing fields have a very irregular distribution pattern.Fishermen often operate from January to July in the area of grid 6005, where the water depths range from 16 to 20 meters.In this location, there are typically 81.27 catches per month.With depths between 11 and 13 meters, Grid 5270 produces about 55.5 catches, with June having the highest catch rates.In the depth range of 6 to 9 meters, Grid 5515 yields 19.45 catches monthly.With an average monthly capture rate of roughly 21.2-27.2%,grids 5760 and 6004 have water depths between 6 and 9 meters and 14 and 16 meters, respectively.4.3-9.5 catches are produced monthly by other grids (Figures 2).

Table 2 .
Lc value indo pacific king mackerel in the waters of the Sulawesi Sea Many tuna fish are caught around Kep. Sangihe Talaut and in the central part of the Sulawesi Sea in deep waters fitted with FADs.Tuna is generally caught in the waters north of Kwandang, north of Manado, and towards the Maluku Sea.Mackerel are generally caught in the waters around a group of islands around Kwandang Bay, such as Otilade Island, Raja Island, and Mocepatlo.Meanwhile, in Tarakan waters, mackerel were caught around Bunyu Island, Mandul Island, Tanjung Harapan, Maratua Island, Sambit Island, Derawan Island, Nunukan Island, and Sebatik Island.