Growth pattern and the condition index of nomei fish Harpodon nehereus captured with mini-trawl in Tarakan Waters

Nomei (Harpodon nehereus) is a which is found in the northern waters of Tarakan City which has a fairly high economic value. The purpose of the study to analyze the growth patterns and condition index of the fish in Tarakan waters. The research was conducted in two periods, namely the period January-February 2022 and June-July 2022. The research method used a quantitative descriptive method. Fish samples were collected from fisher and data observed were total length, total weight, and sex. In January, the sampled H. nehereus consisted of males (n = 69) and females (n = 231) with allometric negative growth and both fat (male = 50.7%) and thin (female = 48.1%) body type were found. In February 2022, the growth of males (n = 70) and females (n = 224) were positive allometric and both type of body shape were found, with sex ratio of male 48.6% and female 51.4%. In June 2022, the growth of males (n = 980) and females (n = 680) were negative allometric with body shape of both fat (male = 48.1%) and thin (female = 48.5%). In July 2022, the growth of male (n=1197) and female (n=822) were negative allometric with body shape fat (male=49.1%) and thin (female 47.8%). A better management of aquatic biological resources, especially the stock of nomei fish (H. nehereus), is crucial for a sustainable resource.


Introduction
Tarakan City is a city with more water area than its land area.From the total area of Tarakan city of 657.33 km 2 , the area of Tarakan City's marine waters reaches approximately 406.53 km 2 while the land area is approximately 250.80 km 2 [1].The marine area of Tarakan City has great fishery potential, this can be seen from the many fishery activities that can be found around these waters, including capture fisheries and aquaculture.Expectedly, the increase in the production of fishery products in Tarakan City until 2021 reached a total of 33,151.95tons/year [2].The people of Tarakan City whose lives depend on fishery product have their hands tied due to various problems revolving the local fishery, mostly due to erratic weather which makes it very difficult to keep track of the stock or even to set out to fish.This causes a fluctuation of price for the nomei fish (Harpodon nehereus) caught in the Waters of Juata, Tarakan City.Nomei fish is an economically important fish as it is widely consumed by the locals.However, fresh consumption only accounts for a small amount, most are processed into dry form for national and international markets [3]; [4].
Nomei fish (H.nehereus) live at the muddy floor of coastal areas, river mouths, and could grow to length of up to 40 cm while it mostly growth to 10-25 cm.Nomei fish are classified as wild with their diet consisting of demersal animals, mostly small fish.Nomei fish (H.nehereus) are local marine fish found in the waters of Tarakan [5].All over the world, Nomei Fish (H.nehereus) are known as the "Bombay Duck" [6].This fish is locally referred to as 'Lotiya Machh' or 'Loitta' around coastal areas of Bangladesh, which is distributed in shallow coastal waters and estuary areas of the Bay of Bengal, Indian Ocean and Arabian Sea [7].This fish is ubiquitous in the Indo-West Pacific Ocean; from India to the Solomon Islands.This species is characterized by its benthopelagic and oceanodromous nature; habiting in both brackish water and sea water, specifically soft coastal waters and estuarine waters.Occupies deep waters off the coast almost all year round, but also congregates at river mouths in search of prey on rainy seasons.This aggressive predator preys on small fish [8].
While it being local to the Tarakan waters, the yield of nomei has decreased in recent years.Continuous capture will impact fisher income negatively and further depletes its stock, eventually leads to extinction, therefore further studies are required [9].Efforts in controlling the nomei fish (H.nehereus) population are carried out to control the number of fish populations in order to remain sustainable.To maintain the number of fish populations that continue to decline due to fishing efforts, it is necessary to study the growth and condition.The study aims to define the growth pattern and condition index of nomei fish (H.nehereus) in Juata Waters, Tarakan City.

Time and place
Research on Nomei Fish (H.nehereus) was carried out two periods, namely in January-February 2022 and June-July 2022 in the sea waters of the Tarakan city.Sampling was carried out 22 times.

Research methods
The research was conducted through a quantitative descriptive case study.Sampling was carried out based on the catch of fishermen using mini trawler fishing gear in the sea waters of Tarakan City.The sampling point were determined through a random purposive method and data collection was done through laboratory-scale methods with parameter recorded being total length, sex, and total weight of H.nehereus.The analysis was carried out at the Fish Biology Laboratory, Faculty of Fisheries and Marine Sciences, University of Borneo Tarakan.Nomei fish (H.nehereus) is not a protected fish species because it is found in quite abundant numbers in the Juata Laut waters of Tarakan city.The fish species H. nehereus by Indonesian Government regulations regarding populations of this type is not included in the limited protection issued by Cites.
The isometric growth condition factor was calculated using the following equation: whereas W = total weight of H. nehereus (g); L = total length of H. nehereus (mm); 10 5 = the equation was taken, so K (TI) value is close to 1.
Condition factor of H. nehereus with allometric growth characteristic was calculated using the following equation: whereas W = total weight of of H. nehereus (g); Ŵ = allegation of total weight of H. nehereus (g); W = a L b obtained using the regression equation of length-weight correlation.

Results and discussion
The results of the growth of Nomei fish H. nehereus caught by fisherm in the waters of Juata, Tarakan City in January-February using a method based on the [18] can be see figure 1 to figure 4 below.Based on the results of the research, 300 individuals of H. nehereus fish were caught in Sea waters of Tarakan City in January 2022 with body weight averaging 40.33 g and total length of 20.19 cm in male H. nehereus fish.The female of H. nehereus has the body weight average of 42.39 g and a total length of 20.69 cm.The analysis of the relationship between length and weight showed that the b value in male H. nehereus was 2.6459 while for female H. nehereus was 2.768, this is indicative of allometric growth pattern (b<3).This means the gain of weight is slower than the gain of length.The growth pattern that occurs is affected by the environmental conditions the organism lives in, as well as resource availability in order to support survival and growth.Food is more impactful on tropical fish growth than water temperature.The success of getting food and the first time the gonads mature can determine and affect growth.When the gonad is in its maturity process, the growth slows because the nutrition allocation is prioritized for gonad development [19].Two hundred and ninety-seven individuals of H. nehereus were sampled with average body weight of 19.99 g (male) and 20.41 g (female), and total length of 37.13 cm (male) and 40.40 cm (female).The regression analysis and its graph on the relationship between length and weight (Figure 2) generated the following equation for male H. nehereus: y= 3.2117x -2.6203 with a b value of 3.2117.While the female H. nehereus with the equation y= 3.1844x -2.5796 with a b value of 3.1844.This indicates that the growth pattern of male and female H. nehereus is allometric negative (b<3) which indicates that the gain of weight is slower than the gain of length.There is a slight difference from the findings of the preceding species observations in Juata and Amal waters which obtained b values of 2.59 and 3.00, respectively [4].This means that there is a chance that individual Bombay ducks in Tarakan waters are getting smaller.These differences can be related to certain variables such as behavioral, spatial, and temporal variations, or the impact of environmental parameters.Some aquatic species are deemed migratory.Migration can affect the reproduction and/or feeding habits of the species.Migratory species may also inhabit different places in relation to their life stage.This affects the spatial distribution of species as well as its morphometric characteristics [20].Adaptive management in the protection and sustainable use of fish in migration is caused by climate change, namely salinity, rainfall, temperature, sea level, and species distribution range [21]; [22].Length-weight relationship (LWR) analysis was done accordingly to the amount of sample expectedly needed to give proper descriptive information on the growth pattern of H. nehereus fish in Juata Sea Waters.The description of the length-weight relationship of H. nehereus was carried out separately between male and female.The number of H. nehereus fish caught during the study was 1,660 individuals averaging 37.58 g (male) and 39.46 g (female) of body weight with total length of 19.93 cm (male) and 20.31 cm (female).Length-weight relationship curve and growth model of H. nehereus can be inferred from the results of the analysis (Figure 3).The fish length-weight growth model is y=2.0402x-1.0873 for male with a b value of 2.0402 and y=2.0293x -1.0789 with a b value of 2.0293 for females.It shows that the value of b obtained is smaller than 3 (b<3), so it can be concluded that the growth pattern of H. nehereus in Juata Sea Waters is allometric negative.This means that the gain of weight is slower than the gain of length.Fish growth patterns are usually influenced by environmental conditions where fish live, as well as the availability of food to enhance the survivability and development of the fish.This is in accordance with the statement by [19], that food is more impactful than water temperature for tropical fish growth.The success of getting food and the first time the gonads mature can determine and affect growth.When the fish are spawning, it will also cause the growth speed to be slow because the food consumed and digested by the fish will first be used for the development of the gonads.The results of the analysis were used to compare a fish population based on sex, as well as to determine changes in fish conditions throughout the year.The amount of H. nehereus fish captured during the study in July was 2,019 individuals with a total weight of 37.35 g (male) and 38.22 g (female) with a total length of 19.15 cm (male) and 19.34 cm (female).The length-weight relationship of male H. nehereus is defined as y = 2.0661x -1.0955 with a b value of 2.0661 and y = 2.1075x -1.1474 with a b value of 2.1075 for females.The value of b was less than 3 (b<3) which indicated negative allometric growth.This means that the gain of weight is slower than the gain of length.The difference in the increase between weight and length in fish, apart from being caused by environmental conditions and food availability, can also be caused by the fish caught being dominated by small fish, which length growth is faster than their weight [23].According to [23], the effect of length and body weight on the b value is quite significant, this means the factors affecting said cause could indirectly affect the b value as well.Condition index are very important parts of growth in analyzing fish populations and can be used to determine fish body shape [15].The results showed that the overall condition index value of the male H. nehereus fish was found to be in the range of 0 to 1.51.The analysis of the condition index on male H. nehereus obtained results of 69 total individuals sampled with the following distribution: condition index of 0.50-0.99(thin) for 32 individuals (46.4%), condition index of 1 (proportional) for a one individual (1.4%), condition index of 1.01-1.50(fat) for 35 individuals (50.7%), condition index of more than 1.51 (fat) for a one individual (1.4%).Figure 5 illustrates that the body shape of the male nomei fish population has a fat and thin body shape that almost dominates the nomei fish population.The number difference between both body type (fat and thin) was small but fat body type still dominated.It can be inferred that the habitat of male nomei fish in Juata waters has sufficient food availability which allowed it to feed, spawn, and live.In addition, the difference in the value of the condition index was caused by variations in the length and weight range of the snakehead fish itself.The variation in size, both length and weight, will affect the size of the fish that will spawn.This is supported by the statement of [25] which states that spawning can be one of the causes of changes in the value of fish condition index.According to the results obtained, the condition index value of male H. nehereus fish ranged from 0 -> 1.51 with a total of 70 individuals, consist of 34 individuals of thin (48.6%), 2 individuals of proportional (2.9%), and 34 individuals of fat (48.6%).Figure 6 illustrates that the body shape of the male H. nehereus fish population is dominated by fat and thin body shapes.The percentage of the body shape of fat and thin male H. nehereus fish has the same value, which is 48.6%.It can be inferred that the habitat of male nomei fish in Juata waters has sufficient food availability which allowed it to feed, spawn, and live.The total of 224 individuals of female H. nehereus obtained during study has condition index value ranging from 0 -1.51, consist of 115 individuals (51.3%) of thin, four individuals (1.8%) of proportional, 104 individuals (46.4%) of fat, and one individual (0.4%) of very fat. Figure 6 illustrates that the body shape of the female H. nehereus is dominated by thin and fat body shapes.The percentage value of the body shape of thin and fat female H. nehereus fish has a small difference of 4.9% and includes the most obtained from the results of data processing.The value of the condition factor can go up and down depending on the spawning season for fish, especially female fish.Variations in the value of the condition factor (K) are largely determined by food, age, sex ratio and gonad maturity level [15].The condition factor value will increase towards the peak closer to spawning and decrease after spawning.This is because the main energy source is used for gonad development and spawning [15].During the research in June 2022, 980 male and 680 female of H. nehereus were obtained.The condition index value of H. nehereus was obtained based on the relationship between length and weight (KTI) of fish ranging from 0.33 -1.51 for males and 0.49 -1.51.The condition index value of H. nehereus differs for each sex: the most percentage of the condition index obtained for males are 46.5% (thin) and 48.1% (fat), while for female are 48.5% (thin) and 45% (fat).The difference in the condition index values was caused by the varying length-weight range of H. nehereus.The various length-weight ranges will affect the size of the fish that will spawn.This is in accordance with the statement of [19] which states that spawning can be one of the causes of changes in the value of the fish condition index.During the research in July 2022, 1,197 male and 822 females of H. nehereus were obtained.Based on the number of samples caught, the male KTI values ranged from 0.31 to 1.51 while the female KTI values ranged from 0.33 to 1.51.The condition index value of H. nehereus varies by sex, base on the result of data processing, the most condition index percentage obtained for male H. nehereus are 46.1% (thin) and 49.1% (fat), while for female are 47.8% (thin) and 47.1% (fat).The index value of fish conditions in waters varies.The various condition index values depend on the diet, age, sex and gonad maturity.In addition, the condition factor can go up and down because it is dependent on the spawning season for fish, especially female fish [23]; [26].The growth pattern based on the length weight relationship for male and female H. nehereus was allometric negative the gain of weight is slower than the gain of length.2. Percentage of condition index values based on the length weight relationship for male H. nehereus is dominated by fat body shape, while for female is dominated by thin body shape.

Suggestion
Further research is needed on the environmental conditions of H. nehereus fish in the Juata Laut area of Tarakan City so that the presence of these fish in these waters can be sustainable and the utilization of fish biological resources is carried out optimally.

Figure 1 .
Figure 1.Log total length and log body weight of male (a) and female (b) nomei fish in January 2022.

Figure 2 .
Figure 2. Log total length and log body weight of male (a) and female (b) nomei fish in February 2022.

Figure 3 .
Figure 3. Log total length and log body weight of male (a) and female (b) nomei fish in June 2022.

Figure 4 .
Figure 4. Log total length and log body weight of male (a) and female (b) nomei fish in July 2022.

Figure 5 .
Figure 5. Percentage Condition index of male (a) and female (b) nomei fish in January 2022

Figure 6 .
Figure 6.Percentage Condition index of male (a) and female (b) nomei fish in February 2022.

Figure 7 .
Figure 7. Condition index of male (a) and female (b) nomei fish in June 2022.

Figure 8 .
Figure 8. Condition index of male (a) and female (b) nomei fish in July 2022.