Yellowstripe scad fishery (Selaroides leptolepis) in FMA 712: a short review

Small pelagic fish caught with mini purse seines (MPS) in the Java Sea has been exploited for a long time and causes resource sustainability. Policies in preserving natural resources require scientific studies that can provide management options. This research was conducted from March to July 2017 at PPN Pekalongan by recording catches and measuring fork length (FL). The composition of the MPS catch showed that 64% were small pelagic and dominated by Goldstripe sardinella (Sardinella gibbosa) 56.3%, Bigeye scad (Selar crumenophthalmus) 19.3%, and the scads (Decapterus spp) 12.3%, other species with small numbers including Yellowstripe scad (Selaroides leptolepis) by 2.5%. This Yellowstripe scad has a length of between 4.5-18.5 cm FL (average of 10.86 cm FL). The estimated natural mortality (M) is less than the fishing mortality (F). The level of exploitation (E=0.70) indicates that it is overfishing. The management operations that need to be taken to preserve the yellowstripe scad are by regulating the fishing area, determining the size of the allowed MPS nets, and limiting MPS attempts in the Java Sea.


Introduction
Small pelagic fish is an abundant resource in Indonesian waters, including in the northern part of Java Island, which is incorporated in the fisheries management area (FMA 712).The production of small pelagic resources in these waters contributes 20% of the national production (DGCF, 2004(DGCF, -2013) ) in [1].The abundance of resources in the Java sea waters is supported by the characteristics of waters rich in nutrients from rivers along the north of Java [2].It was stated by [3] that the exploitation fisheries in this area from 1968 to 1980 used trawler fishing gear to catch shrimp and demersal fish, but after 1980 there was a change to purse seine.Purse seine fishery is considered the most effective fishery in exploiting small pelagic resources [4].A purse seine is fishing gear for catching pelagic fish in groups such as mackerel, Indian oil sardine, scads, tuna, skipjack, and others [5].However, the increase in fishing using purse seines will ultimately have an impact on the sustainability of small pelagic fish resources [1,6,7].There has been a decrease in the productivity of purse seine vessels, which indicates the shrinkage of small pelagic resources in the waters of the Java Sea [8].Small pelagic fish migrate to find food, spawn, and habitats with temperatures and environments suitable for their lives [2].Various small pelagic fish, including the scads, mackerel, Indian mackerel, Goldstripe sardinella, spotted sardinella, and others, were targeted for the catch, including the yellowstripe scad (Selaroides leptolepis).The yellowstripe scad is a target for catching because it is often used as food such as pindang, grilled fish, and salted fish [9].This fish includes mesopelagic, a species of the family Carangidae with a distribution area in the Indo-Pacific region with a flat and elongated body shape [10,11].However, although the fish are commercial, their numbers do not exceed 10% of the total pelagic fish in the waters and are dominantly found in coastal rather than offshore areas [3].This fish is often caught in large numbers because it attracts bright zones to keep schooling [12].
Fishing by schooling put pressure on fishing resources.In general, the exploitation of small pelagic fish in FMA 712 based on the Decree of the Minister of Marine Affairs and Fisheries Number 19 of 2022 concerning the Estimation of Potential Fish Resources, Amount of Permissible Fish Catch, and Level of Exploitation of Fish Resources in the State Fisheries Management Area of the Republic of Indonesia is still in the moderate stage (E = 0.4).However, a resource assessment still needs to be done as a basis for management because the increase in fishing pressure affects the change structure population and the level of exploitation which can also disrupt the condition of resource stocks in the waters [13,14].Many studies on the management of purse seine fishing activities in the Java Sea (FMA 712) have been operated, but they do not specifically discuss the yellowstripe scad (Selaroides leptolepis) and its exploitation rate [1,6,[15][16][17].Therefore, this study analyzes the MPS fishery's condition and the yellowstripe scad's exploitation in the waters of FMA 712, which can be used as a basis for making management policies.

Data collection
This study was conducted for 5 (five) months, from March to July 2017, at PPN Pekalongan.This location was used as central data collection because it is the largest landing center for small pelagic fish and mini purse seines (MPS) in North Java.Small pelagic fishing areas in these waters are presented in Figure 1.Data collection activities involved researchers with the assistance of enumerators who observed ships and recorded catches ashore with mini purse seines.Observations and measurements were also conducted on the fork length of the yellowstripe scad (Selaroides leptolepis) as many as 3,641 using measuring paper with an accuracy of 0.5 cm.

Data analysis
The catch was analyzed by identifying various types of caught fish, especially small pelagic fish.The catch rate is analyzed by comparing the total catch production (Tons) with the effort (units) of the vessels used in fishing activities.The next stage is the distribution of fish size structure depicted in the form of a graph with a class interval of 1 cm.Analyzed the average catch size (Lc) by determining the intersection point between the 50% cumulative frequency curve and the fish length [18].The value of growth rate (K), asymptotic length, and theoretical age on fish length is equal to zero using a literature study from [19].Analysis of total mortality (Z), natural mortality (M), and fishing mortality (F) using equation [20], with the correlation coefficient of length and weight (b) in the waters of the Sunda Strait b = 2.7871 [21], Ci = 0.302 for fish pelagic and tmax were analyzed by equation [22].

Fishing characterization, catch composition, and catch rate
Catching small pelagic fish for mini purse seines (MPS) in these waters uses a wooden boat weighing 28 GT and is equipped with a 16 PK engine.The ship has six units of hatches, each with a capacity of 1.5 tons.This ship used a mini purse seine (MPS) fishing gear with a net size of 200 x 20 m with a mesh size of 2.5 inches and made of nylon.This fishing gear is usually operated at a depth of 20-30 m with several crew members (ABK), as many as 20 people.The difference in size and material purse seine vessels used in other waters, such as Maluku, which is made of fiberglass with a length of 23.68 m and a width of 6.12 m [23].Meanwhile, in the waters of the Sunda Strait, vessels measuring 12-15 GT are used with one day of fishing time [9].So the difference in materials and specifications of the ship is influenced by the conditions of the waters, length of time of catching, and fishing gear size used.Furthermore, the catch rate of mini purse seine vessels operating in these waters is, on average, 2.84 tons/unit (Table 1).The catch rate is related to the production and effort of mini purse seine vessels that carry out fishing activities.The catch rate also provides an overview of the condition of the availability of resources in these waters.Fluctuations in catch rates are influenced by weather, such as wind speed and waves because the catch in the east monsoon is higher than in the west monsoon [2].Sea surface temperature and chlorophyll-a in the waters also influence the catch rate due to several types of fish such as Goldstripe sardinella, Spotted sardinella, and others [24].However, according to Sadhotomo et al. (1986) in [8], the number of days at sea also strongly influences changes in catch rates.It is even added by [25] that the engine power (PK) and the fishing gear size affect the production of purse seine vessels.However, the level of effort and stock of resources in the waters is considered the most significant contributor to production and fishing efficiency [26].However, fishing gear size, the size of the vessel, and the number of days at sea contribute to production and fishing rates.The catch obtained by mini purse seine fishermen was dominated by small pelagic fish, as much as 64%, demersal fish 19%, squid, 12%, and large pelagic fish, 5% (Figure 2).This catch is still in line with previous studies in the same waters, which is dominated by small pelagic 52-56.53%[1,4,6], which shows that this resource is still a leading commodity.The catch in the waters of the Java Sea differs from that caught in the Maluku Sea, in which large pelagic fish dominate and small pelagic fish only become bycatch [23].The difference in fishing locations is a determining factor for the type of fishery production produced, even though the fishing gear used is the same type [27].Small pelagic fish resources are also sensitive to the environment, especially salinity, so their production is also related to aquatic environmental conditions [5].
Furthermore, the composition of small pelagic fish caught was dominated by Goldstripe sardinella (Sardinella gibbosa) 56.3%, Bigeye scad (Selar crumenophthalmus) 19.3%, and the scads (Decapterus spp) 12.3%.Several other species were few, including the yellow-tailed fish (Selaroides leptolepis) at 2.5%) (Figure 3).However, the composition experienced a shift in 2002-2007, dominated by the scads (Decapterus russelli and Decapterus macrosoma) as much as 52% [6].This composition was also found in the same waters, including the scads (22%), Goldstripe sardinella (21%), mackerel (16%), Indian mackerel (14%), Indian oil sardine (11%), and large pelagic fish (7 %) [16].This shift in composition can also occur due to the different fishing seasons for small pelagic fish in the Java Sea, both east and west monsoons [17].This fishing season is also closely related to the catchment area because the spatial distribution of small pelagic fish in the west season is in the western part of the Java Sea waters and vice versa in the east season [2].Even the sea surface temperature influences the production and types of fish caught [24].The scads dominate the catch in Bone Bay by 55.2%, and in the Flores Sea, it is dominated by large pelagic fish, namely tuna, by as much as 39.8% [27].This showing that the composition of the catch is a description of the ecological conditions of a fishing area because it shows the types of fish that can adapt to that environment [28].So the composition of the catch is closely related to the season, the fishing ground, and the environment.

Size structure and resource use
The size structure of Selaroides leptolepis that has been caught was between 4.5-18.5 cm FL with the dominant mode at 11.5 cm FL (Figure 4).This size is still smaller than those caught in the waters of Tomini Bay between 9.5-22.2cm TL, Wondaman Bay 10-24 cm TL, Ternate 8.2-21.7 cm TL and 5.65-31.82cm TL and larger than in the Sunda Strait waters 9-18 cm TL and Matang Malaysia 9-17.5 cm TL [21,[29][30][31][32][33].The difference in the size structure of the caught fish can be caused by differences in fishing gear and mesh sizes used in various waters [13].
The average catch size (Lc) in these waters was 10.86 cm FL (Figure 5), which indicates that the caught fish were still young.This Lc was compared to the size of the first gonad maturity (Lm) in the waters of the Sunda Strait for females 12.19-13.46cm and males 13.41-15.97cm and 18.9 cm in Manado Bay [11,34,35].If this condition is not controlled, the population of the resource will decrease because that specific species is not rising in the waters.Although gonad maturity is influenced by various things, such as water conditions, environment, food, and predators, the management in catching fish must comply with the standard size proper for catching.Furthermore, the value of natural mortality (M) is lower than the fishing mortality (F), indicating that the exploitation of yellowstripe scad in these waters is high.The fish exploitation rate is E = 0.70 (Table 2), which suggests that it has been overfished by 20% from the ideal condition of E = 0.50 [36].This exploitation rate serves as a control to prevent a decrease in the population stock of aquatic resources.There are 2 (two) types of overfishing conditions, (1) growth overfishing, which is a condition where caught fish are still young, and (2) recruitment overfishing, when fish are in parental conditions and about to be spawned [37].So based on this analysis, we must make production management by reducing the catch by 40% from what is currently done.Various management policy efforts can carry out by controlling the number of fishing fleets, the mesh size, and determining the appropriate size to catch [13].However, each water has different fishing characteristics, including dominant resources.The condition of the MPS fishery in the Java Sea, which small pelagic fish dominantly catch, must pay attention to the survival of this resource.Many caught fish still in a young condition indicates that the sustainability of the resource may decrease because there has not been an increase in the number of individuals in the waters.Thus, controlling the number of MPS fishing vessels, the size of the nets, and the fishing grounds are things that can do in the management of small pelagic fish, especially yellowstripe scad, in the Java Sea waters.

Conclusion
Small pelagic fishing vessels operating in the waters of the Java Sea (WPP 712) are wooden vessels with a capacity of 28 GT with a mini purse seine fishing gear.The catch rate of MPS in these waters is 2.84 tons/unit, with monthly fluctuations related to the number of vessels.The dominant catches were small pelagic resources of 64%, with the most fish species being Goldstripe sardinella (Sardinella gibbosa) at 56.3%, bigeye scad (Selar crumenophthalmus) at 19.3%, and the scads (Decapterus spp) 12.3% and yellowstripe scad (Selaroides leptolepis) about 2.5%.The mode size of the yellowstripe scad caught is 11.5 cm FL with the average catch size at 10.86 cm FL.Natural mortality (M) is lower than fishing mortality (F) which causes an increase in exploitation (E) of 0.70, meaning that it has encountered overfishing.The management production is by reducing 40% over controlling the number of vessels, mesh size, and fishing grounds.

Table 1 .
The catch rate of mini purse seine boats in Pekalongan.

Table 2 .
Parameters of mortality and exploitation rate.