Biological aspects of squid (Loligo edulis) in the waters of Eastern North Sumatra, Indonesia

DOI:10.13170/depik.12.1.28602 Squid is one of the non-fish resources that have economic value and is a target species in demersal fisheries activities with squid fishing gear and stick-held deep net. This research aims to determine the biological aspects of squid (Loligo edulis) such as length frequency distribution, length-weight relationship, sex ratio, gonadal maturity level, gonadal maturity index, size at first caught, and size at first maturity of the gonads. The method used in this research was a descriptive survey. The sample collection method used systematic random sampling and purposive sampling techniques. This observation was carried out on March 7 to July 30, 2022, at the Belawan Ocean Fishing Port and Tanjung Balai Port. The results showed that the average length distribution of squid was 17.73 cm. The relationship between the length and weight of squid is negative allometric. The sex ratio is 1:1.05. The negative allometric growth pattern is dominated by Gonadal Maturity Level (GML) I and GML II. The highest GML value for male squid was 2.06% at GML III, and the highest GML value for female squid was 1.92% at GML III. The average size of the caught squid length (Lc) is 10.42 cm. The size of the first gonad maturity (Lc) was 13.32 cm.


Introduction
Geographically, the waters of the Malacca Strait are part of fisheries management areas (WPP) 571 (Arsana, 2014) The northeastern area is directly adjacent to Economic Zones (EEZ) waters of Malaysia, Thailand, and Singapore, the southwest is administratively bordered by the three provinces of the east coast of Sumatra namely the southwest is administratively bordered by the three provinces of the east coast of Sumatera (Aceh, North Sumatera, and Riau) to the northwest to the waters of the Andaman Ocean and the southeast to the waters of the southern Natuna Ocean.This region, based on the estimation of fish resource potential (FRP), has 9 (nine) FRP groups, namely large pelagic fish, small pelagic fish, demersal, penaeid shrimp, consumable crayfish, lobsters, crabs, and squid (Faizah and Sadiyah, 2019).
This region stretches along the east coast of North Sumatra.The east coast of North Sumatra has a 545 km coast and consists of 7 regencies or cities, namely Langkat Regency, Medan City, Tanjung Balai City, Asahan Regency, Labuhan Batu Regency, Deli Serdang Regency, and Serdang Bedagai Regency.The East Coast of North Sumatra is a busy shipping lane and one of the areas for fishing activities, especially in Belawan Waters.Belawan is a magnet for North Sumatra's fishing activities (Tambunan et al., 2010).
The fishery resources in the east coastal area of North Sumatra consist of fish and non-fish resources.One of the non-fish resources is squid.Squids are invertebrates that are classified as pelagic but are sometimes classified as demersal due to their frequent bottom presence.They are members of the mollusk phylum's cephalopod class (Faradizza et al., 2019;Surachmat, 2018).Squid fisheries are now one of the potential non-fish resources that have important economic value and are widespread in Indonesian waters (Nababan et al., 2017).The tools Depik Jurnal Ilmu-Ilmu Perairan, Pesisir dan Perikanan Volume 12, Number 1, Page 40-48 Zulkifli et al. (2023) used are squid nets, stick-held deep nets, squid fishing rods, and by-catches from ring trawls and fish trawls (Ilhamdi and Yahya, 2017).
The increasing intensity of fishing and the number of fishing fleets as well as the modernization of fishing gear can lead to overfishing.In addition, the high rate of degradation of spawning habitats, the enlargement of squid in coastal areas due to pollution, environmentally unfriendly fishing, sedimentation, and land conversion as a result of development can result in a reduction in squid populations (Baskoro et al., 2017).
Squid (Loligo spp.) caught in the waters of Eastern Sumatra is mostly landed at Belawan Ocean Fishing Port (PPS Belawan) and Tanjung Balai Asahan Port.Data on squid catches and fishing efforts in the Eastern Waters of Sumatra landed in Belawan Ocean Fishing Port (PPS Belawan) from 2016 to 2020 on the ecological dimension, technological dimension and social dimension are included in the category of less sustainable (Chairunnisa, 2022).
The need to maintain squid resources (Loligo spp.) is to maintain the potential of squid to be optimally utilized so that there is no overfishing.Therefore, it is necessary to study the basic information on biological aspects, aspects of capture fisheries, and management efforts to support efforts to manage squid resources (Loligo spp.) sustainably and the creation of sustainable and environmentally friendly fishing.
Based on the explanation above, it is necessary to conduct research that aims to analyze various aspects of squid biology and reproduction, including length frequency distribution, length-weight relationship, sex ratio, gonadal maturity level (GML), gonadal maturity index (GMI), the length of the first maturity, and the length of first captured.

Location and time
This research was carried out from March to May 2022 which months are known as transitional seasons (Ariyanto et al., 2021) and was located at two squid landing locations in the eastern region of North Sumatra which include: 1. Belawan Ocean Fishing Port, Bagan Deli Village, Medan District Belawan City, North Sumatra Province 2. Tanjung Balai Asahan Port, Bagan Asahan Village, Tanjung Balai Teluk Nibung District, North Sumatra Province.Sampling activities are carried out every day, where 1.5 months are located in Belawan Ocean Fishing Port and the remaining 1.5 months are located in Tanjung Balai Asahan Port.

Data collection
The tools and materials used during the observation are shown in Table 1.The data collection method during this research is a direct survey method, namely by looking at and making observations in the field of squid samples that are the target of observations.The data retrieved are primary data and secondary data.
Primary data are obtained from the field such as measurements of length and weight, gender, gonadal maturity level, and others.As well as conducting direct interviews with fishermen or respondents using the questionnaires that have been provided (Mustaqim, 2016;Daud et al., 2020).
Squid sampling (L.edulis) used a random sampling method.Dissected sampling was taken using the purposive sampling method Data analysis

Squid mantle length frequency distribution
The length frequency distribution is obtained by determining the class interval, middle grade of the class, and the predetermined length frequency distribution in class intervals then calculated using descriptive statistics then presented in the form of graphs (Selvia et al., 2019).

Relationship between length and weight
Measurements of total length and weight were performed to compare eating habits based on groups of class length measures (Ismail et al., 2013).According to Perangin-angin et al. (2015) the steps to determine the structure of the catch population using data on the length of the mantle are as follows: 1. Specifies the class range (J), with the formula: Range = largest data -narrowed data l 2. Specifies the number of interval classes (C), with the formula: C = 1 + 3.3 log n (n = number of samples)  Zulkifli et al. (2023) 3. Determining the length of the class interval (C), using the formula: C = Range/Number of Interval Classes 4. Enter the length of each specimen instance in a predetermined class.The relationship between length and weight uses a linear allometric model.This model is used to calculate parameters a and b through measurements of length and weight (Brinkman, 1993): W = a L b Information: W: Individual weights of squid (g) L: Mantle length (cm) a. Intercept (intersection of the curve of the relationship of the length of the weight with the y-axis) b.Slope Linear or straight-line equations are obtained from the following equations: Parameters a and b were obtained from Regression Analysis with Ln W as 'y' and Log (i) as 'x', so the regression equation is obtained as follows: y = a + bx(i) (Muhsoni, 2019).The coefficients of determination and correlation can also be determined through equations.
In this analysis of weight length relationships, what needs to be considered is the value of b which can be interpreted as follows: 1. b < 3: Length gain is faster than weight gain (negative allometry) 2. b = 3: Length gain balanced with weight gain (isometric) 3. b > 3: Weight gain is faster than length gain (positive allometry) (Perangin-angin et al., 2015) To determine the growth pattern, Bailey's t-test was needed (Thomas, 2013;Nair et al., 2015).The ttest was run to determine significant differences from the isometric value (b = 3) with significant level at 5% (P < 0.05).The formula of Bailey's t-test is as follows (Fauziyah et al., 2021): Information:   = Bailey's t-test, b = the slope of the linear regression Sb = standard error of the b coefficients The correlation coefficient (r) to see the closeness of the relationship between length and weight is obtained from the formula bellows (Nurhayati et al., 2016).
r= √ r 2 Information: r: Correlation coefficient is an abstract measure of the degree of closeness of the relationship between x and y (-1 < r < 1); 1 means that there is a close and positive relationship; -1 means that there is a close and negative relationship; and 0 means that there is no close relationship.

Length of first captured (Lc)
Length of first captured according to (Sparre-Venema, 1998): The Lc value is obtained by plotting the percentage of the cumulative frequency of squid caught by its standard length size, where the cut-off point between the curves of 50% cumulative frequency is long when 50% of squid are caught (Tirtadanu and Ernawati, 2016) the value of Lc can be calculated through the formula:

Length of first maturity (Lm)
The size length of the first maturity is a variable of the reproductive strategy in squid, besides the sex ratio and spawning periods and types (Barokah et al., 2016).Calculation of the length of the squid length of the first maturity (Lm) using the Spearman-Karber equation method developed by Udupa (Abubakar et al., 2019): Information: m: Logarithms of a length class at the first maturity d: The difference in the logarithm of the addition of the mid-length value k: Number of length classes xk: Logarithm of the mid-value of the length of the fish that has matured gonads (Pi=1)

Sex ratio
According to (Fisher, 1930) the ratio of male to female individuals is estimated at 1:1 naturally in water with a normal spreading population.The equation used to calculate the sex ratio is as follows: Sex Ratio= n J n B Information: n J: The number of male squids (individuals) n B: The number of female squids (individuals) To find out whether there is a real difference between the comparison of male and female individuals, it is carried out through testing and testing 'X 2 ' (chi-square) with a formula according to (Legendre and Legendre, 2003;Mchugh, 2013): = The cell Chi-square value ∑χ2 = Formula instruction to sum all the cell Chi square values χ2i-j = i-j is the correct notation to represent all the cells, from the first cell (i) to the last cell (j) The value of χ2 obtained from this calculation compared with the value of χ2 in the table with a confidence level of 95% and a free degree (FD) = 1 (one) with the hypothesis: H0: There is no noticeable difference between the number of male and female squid H1: There is a noticeable difference between the number of male and female squid If, Χ 2 calculate < χ2 table = H0 Accepted, H1 rejected Χ 2 calculate > χ2 table = H0, Rejected, H1 accepted.

Gonadal maturity level (GML)
The basis used to determine GML morphologically is the shape, length, color, and development of the gonadal content.Classification of the gonadal maturity level of squid is suggested (Lipiński and Underhill, 1995) in Table 2.

Gonadal maturity index (GMI)
Determining the GMI value of fish can be used the formula below (James et al., 2010): Information: GW: Gonadal Weight (grams) BW: Squid Body Weight (grams) GMI: Gonadal Maturity Index

Biological aspects of squid
The morphological features of the squid obtained are elongated cylindrical shape and the back is tapered with a pair of triangular-shaped fins.Squids found have soft bodies, a pair of eyes next to the head, and five pairs of arms, where one pair of arms is longer than the other called tentacles.The squid found at the research location is shown in Figure 1.The maximum and minimum values of squid mantle length are presented in Table 3.

Weight length relationship
The relationship between the length and weight of the squid is presented in Table 4.

Sex ratio
The squids that were taken from 2 locations as samples were 80 squids.The samples were dissected to see the characteristics of the gonads which consisted of 42 female squids (53%) and 38 male squids (47%) with a sex ratio = 1.05:1.
To find out whether the squid is in ideal conditions to maintain its sustainability, it is necessary to test the sex ratio value.This test uses a chi-square test with a free degree (FD) 1 and a confidence level of 95 % presented in Table 5.

Gonadal maturity level (GML)
A sampling of the overall maturity level of the gonads dissected was 80 samples from 805 squid samples measured and weighed obtained from fishermen in the eastern waters of North Sumatra.From the level of gonadal maturity of 80 dissected sample squid caught in the eastern waters of North Sumatra, a level of gonadal maturity varies from GML I to GML IV.The followings are the male GML of squid caught in the Eastern Waters of the Island of Sumatra shown in Table 6.

Gonadal maturity index (GMI)
Based on the results of the observation that the range values of the Gonadal Maturity Index (GMI) of male and female squids at the research location showed varying amounts.The gonadal maturity index chart is presented in Figures 3 and 4.

Length at first capture (Lc)
The following is a graph of the size first caught on a squid (L.edulis) caught in the waters east of the island of Sumatra presented in Figure 5.

Length at first maturity (Lm)
Statistical calculations using a confidence level of 95% to estimate squid (L.edulis) that have entered the maturity category of gonads are presented in Table 7.The size of the first maturity squid gonads is presented in the diagram in Figure 6.

Discussion
Figure 2 shows the frequency of squid class length landed at 2 squid landing locations in North Sumatra Province totaling 805 squids with a mantle length (cm) ranging from 8-47 cm with an average of 17.73 cm, and a weight range between 26-728 grams with an average of 188.65 grams.The most caught squids ranged from 12-15 cm mantle length class interval of 238, while the fewest caught squids ranged from 3 mantle length class interval.
The average length of this mantle is much bigger when compared to the same type of squid caught in the waters of Belanakan Subang from November 2005 -June 2006.The average length of the L. edulis mantle caught in Belanakan Subanga at 16.5 cm (Puspasari and Triharyuni, 2013).The difference in size between squid landed at the Ocean fishing port of Belawan and at Tanjung Balai Asahan Port in 2022 and squid landed in Belanakan Subang in 2005-2006 can be caused by several actors, including the differentiation of fishing gear.
Squid landed at the ocean fishing port of Belawan and Tanjung Balai Asahan Port is the catch of squid fishing rods and stick-held deep net (Reza et al., 2019) which operates in areas about 12 miles from the shore, with only a small operating time.Meanwhile, the squid that landed in Belanakan in 2005 was caught by purse seine and danish seine operating on the high seas with the help of lights (Puspasari and Triharyuni, 2013).The lamps used have a power of 750-1.500watts and amount to 24-90 pieces (Triharyuni et al., 2012).
According to Tasywiruddin (1999), small-sized squids are more commonly caught in waters farther from the coast and small-sized squids are more phototaxis when compared to large-sized squids so that when caught using the help of light, small squids will be caught more.Thus the difference in size that occurred in squid landed in Belanakan in [2005][2006] with squid landed at the ocean fishing port of Belawan and Tanjung Balai Asahan Port in line with the results of his research.
The maximum and minimum values of squid mantle length being presented in Table 3 can be explained as follows: Squid samples (L.edulis) measured in two locations, namely the Belawan Ocean Fishing Port, totaled 45 squids consisting of 25 female squids and 20 male squids, while in Tanjung Balai Asahan Port 35 squids were consisting of 17 female squids and 18 male squids.The average difference in length obtained in the two locations is in Belawan Ocean Fishing Port of 18.25 cm with a length class interval range of 8-46 cm and Tanjung Balai Asahan Port of 17.05 cm with a length class interval range of 8-41 cm.The difference is not so significant from the size of the squid mantle length in the two areas because the conditions in both environments and the fishing gear used are almost the same.
The relationship between the length and weight of squid presented in Table 4 shows that the calculated T value is greater than the T-table which can be interpreted as rejecting the null hypothesis (H0) by showing a negative allometric growth pattern.The equation of the relationship between squid weight lengths in two research locations caught in the eastern waters of North Sumatra is W = 0.5640L 1.9797 with b = 1.9797where the value of b < 3 (negative allometric) which means that the increase in squid length is greater than the increase in squid weight.The correlation value of the squid weight length relationship is R² = 0.8935 with a value close to 1 which means that the weight length relationship is very closely related (Budiwanto, 2017).
The sex ratio of fish can be used as one of the parameters to give an idea of the abundance (Kudale and Rathod, 2016) and balance of fish in the water (Wujdi and Wudianto, 2013).The results of the squid's sex ratio shown in Figure 4 explained that there are 42 female squids (53%) and 38 male squid (47%) by comparison of sex ratio = 1.05:1.The above conditions according to Limbong and Rahmani (2022) illustrate that the condition of the eastern waters of North Sumatra will quickly recover from fishing activities.Tampubolon et al. (2019) furthermore revealed that the ratio of squid populations as shown in Figure 4 in water where the number of male and female fish is balanced, or more female fish will recover faster than a population dominated by male fish.
Based on Table 5,  2 calculation <  2 table, then Ho was accepted, which means that there is no noticeable difference between the number of male squids and female squids caught and obtained.The findings in the field show that the ratio of females and males is balanced according to Ayorbaba et al. (2019).
The maturity level of the male squid gonads obtained during study was dominated by GML I and only a small part of the mature gonads (GML III and IV) were 15 individuals.While the maturity level of the female squid gonads obtained during the study was dominated by GML II and III only a small part of the mature gonads (GML IV) were 9 individuals, see (Figure 6).There are differences in the phase of maturity of the gonads between males and females.It means that the squid is in the gonadal maturity phase every month, it is suspected that the squid spawns throughout the year, while the peak takes place in March and April.
Figures 3 and 4 above showed that the gonadal maturity index (GMI) of male and female squid shows variations.The highest male squid GMI value was found in GMI III at 2.06% and the lowest at 1.66% in GMI I, and the highest female squid GMI value was at GMI III at 1.92% and the lowest at 1.61% in GMI I.
The most dominant GMI was GMI III, both male and female.Where, the GMI value of male squid is greater than the GMI value of female squid (2.06% > 1.92%), which means that when mature, the male squid gonads tend to have a greater weight than female squid because the more mature the gonads had the squid's body will be heavier and will decrease during the reproductive process gradually.The results of the research cnducted at the research site are the same as the result of the study by Perangin-angin et al. (2015).
The gonadal maturity index (GMI) needs to be done because it can know changes in the gonads quantitatively (Satyani, 2017).GMI growth is directly proportional to GML, meaning that the higher the GML value, the higher the GMI value (Muharam et al., 2020).When spawning will occur, the GMI will increase in value and reach the maximum limit and will decrease after finishing working (Ridho and Patriono, 2016).The weight of the gonads was weighed using analytical scales, then the weight of the gonads was compared with the weight of the body and the result was obtained in the form of a percent (%) (Pane and Hasanah, 2019).
The results of the analysis presented in chart 9 above show that the size of the length of the first captured (Lc) squid as a whole, which amounted to 350 sample squid caught using stick-held deep nets (squid net) fishing gear in the waters east of North Sumatra, was 10.42 cm.interval size range of the mantle length is 8 -47 cm with a mode in the class of 13.5 cm.Compared to the results of research conducted (Pertiwi et al., 2022), Lc value at the study site (10.42) is smaller than Lc at Tasik Agung Rembang Beach Fishing Port (12.53).This condition shows that there is a higher catch pressure at the study site than at the Tasik Agung Rembang Beach Fishing Port.Efforts that need to be made to the above conditions are to limit arrest attempts by issuing regulations related to this matter.While the remaining 455 squid samples were captured using fishing gear which was not included in the Lc calculation because the data used to calculate Lc only used net fishing gear.
It is explained in Table 7 above that the results of the calculation of the analysis of the size of the first maturity squid gonads dissected were 13.32 cm.This size range shows that squid has entered the category of mature gonads (range length) between 12.79 to 13.91 cm.Zulkifli et al. (2023) Based on the calculation results in Table 6, the value of Lc < Lm or it can be interpreted that the squid is not yet suitable for catching and could grow and spawn before being caught.They can also still increase the population of water.In other words, the squid caught has not had time to spawn first.Research conducted by (Pertiwi et al., 2022) at the Tasik Agung Rembang Beach Fishing Port for squid showed an Lm value of (16.50 cm) where this result was greater than the Lm from the place of study location (13.32).This condition shows that the habitat in the Tasik Agung Rembang Beach Fishing Port area is better than the location where the research was carried out.
The comparison in the two places shows that the Lc obtained is smaller than the Lm where which shows that the squid is not yet suitable for catching and could grow and spawn being caught.They can also still increase the population of water.In other words, the squid caught has not had time to spawn first.

Conclusion
The most captured squid ranges in the interval of the mantle length class of 12 -15 cm, while the least caught squid ranges in the interval of the mantle length class 44 -47.Squids grow allometrically negatively, with a balanced sex ratio of 1:1.05.The maturity level of gonads in male squid shows that GML I is the most dominant (42%), while for females GML II is the most dominant (35.71%).The differences in the phase of maturity of the gonads between males and females mean that the squid is in the gonadal maturity phase every month.It is suspected that the squid spawns throughout the year.The Lc value is smaller than the Lm value (12.45 cm < 13.34cm), which indicates that the caught squid has not had time to spawn first.

Figure 3 .
Figure 3.The gonadal maturity index (GMI) of male squid gonads caught in the eastern waters of North Sumatra.

Figure 4 .
Figure 4.The gonadal maturity index (GMI) of female squid caught in the eastern waters of North Sumatra.

Figure 5 .
Figure 5.The length of the first capture of squid at two study locations.

Figure 6 .
Figure 6.The size of the first maturity squid gonads caught in the waters east of North Sumatra.

Table 1 .
Tools and materials.

Table 2 .
The microscopic sexual maturity scale applied for Loligo edulis.

Table 4 .
The weight length relationship of squid (Loligo edulis) captured.

Table 5 .
Chi-square test of squid sex ratio at two locations.

Table 6 .
The gonadal maturity level of squid.

Table 7 .
Length of squid mantle when first maturity gonads (Lm) obtained.