Tuna Growth Coefficient Asymptote Length Mortality Exploitation Yield Per Recruitment This study aims to determine the population dynamics of tuna including age group, growth, mortality, exploitation rate and yield per recruitment. It was conducted from June to August in West Waters of South Sulawesi. By method of age group using Bhattacharya method with FAO-ICLARM Fish Stock Assessment Tools II (FISAT II) program, growth using Von Bertalanffy’s equation, natural mortality (M) using Pauly’s empirical equation, total mortality (Z) using Beverton and Holt’s equations, fishing mortality (F) by the formula Z = F + M, exploitation (E) using Baverton and Holt’s equations and yield per recruitment (Y/R’) using Baverton and Holt’s equations. The results of research of tuna observed were 737 includes 355 male tunas and 382 female tunas. The estimation of total length ranging from 215 mm to 429 mm. Male tunas are classified into 4 (four) of age groups with a length of 236.67, 272.8, 326.04 and 375.53 mm, respectively. Asymptote length (L∞) = 455.00 mm, growth coefficient (K) = 0.33 and theoretical age (t0) of -0.2377 per year. Total mortality rate (Z) = 1.12 per year. Natural mortality (M) = 0.41 per year, fishing mortality (F) = 0.71, exploitation (E) = 0.63 and yield per recruitment (Y/R’) = 0.0691, while male tunas are classified into 5 (five) of age groups with a length of 235.73, 272.86, 326.89, 360.89 and 408.89 mm, respectively. Asymptote length (L∞) = 453.50 mm, growth coefficient (K) = 0.42 and theoretical age (t0) of -0.1853 per year. Total mortality rate (Z) = 1.35 per year. Natural mortality (M) = 0.48 per year, fishing mortality (F) = 0.87, exploitation (E) = 0.64 and yield per recruitment (Y/R’) = 0.0784. Thus, it can be concluded that tuna in West Waters of South Sulawesi have declined and thought occur overfishing.
## 1. INTRODUCTIONPelagic fish production in the western waters of South Sulawesi reaches 55.6%. The percentage of production indicates the availability of pelagic fish in the West Waters of South Sulawesi is greater than other coastal waters in South Sulawesi (Nelwan, 2010). One of pelagic fishes found in the western waters of South Sulawesi which has high economic value is tuna, because the level of market demand is increasing every year. This because tuna fish is much favored by the community, especially those in Lero village of Pinrang district so that this fish is one of the fisheries that are targeted by fishermen. According to statistics from the Marine and Fisheries Office of Pinrang (2017), it shows that the production of tuna in Pinrang has increased from year to year. In 2014, tuna production was 223 tons, in 2015 it was 931 tons, and in 2016 there was an increase in production reaching 965 tons. Based on these data, it can be seen that the production of tuna during the last 3 years, namely in 2014 - 2016 in Pinrang district experienced a significant increase, it because the fishing rate of tuna is getting higher. For the potential of tuna in Western Waters of South Sulawesi can be utilized optimally, sustainably and avoid overfishing, a study on population dynamics can be used as a reference in the development of fisheries resource management, so that the intended utilization of fisheries resources can be realized. This study aims to determine some dynamic parameters of tuna population including age group, growth rate, mortality, exploitation rate and yield per recruitment (Y/R) in Western Waters of South Sulawesi. The benefit of study is to provide information about tuna in Western waters of South Sulawesi and it can be a consideration in planning and management of tuna, to realize optimal and sustainable use of resources and can be used as information material for further research. ## 2. METHOD OF RESEARCHThis study was conducted in June 2019 until August 2019. Sampling of sample fish was carried out in the waters of Makassar Strait, Pinrang district of South Sulawesi (Figure 1).
## 2.1. TOOLS AND MATERIALSThe tools used was a measuring ruler with a precision of 0.1 cm to measure the total length of fish body, stationery used to write research data in the field, surgical instruments to dissect the fish and a camera for documentation of activities in the field. The material used was tuna obtained from the Western Waters of South Sulawesi as a research sample. ## 2.2. COLLECTING SAMPLE FISHSampling of tuna comes from overall catch of fishermen every day in the Western Waters of South Sulawesi (Figure 1) The fishing gear used by fishermen is fishing line. Sampling was done every day during June to August 2019. Furthermore, the fish samples were taken to measure the total body length starting from the front end of the head to the tip of the caudal end using a ruler in 0.1 cm precision. Then, the fish is dissected and the gonads are observed to determine their sex, based on the color and the average temperature data of Western Waters of Sulawesi South obtained from the Meteorology, Climatology, and Geophysical Agency of Makassar. ## 2.3. AGE GROUPThe age group is determined by using Bhattacharya’s method
with FAO-ICLARM Fish Stock Assessment Tools II (FISAT II) program. The first,
the procedure for determining age groups is determine the class length, frequency
and middle class. The number of cohorts, and the average length of individuals
in each age group were obtained by using a long frequency difference, i.e fish
were divided into long classes which then find the difference between the
highest and lowest values of a class with the previous class. One
age group ( ## 2.4. GROWTHGrowth rates related to fish length follow Von Bertalanffy’s growth equation (Sparre and Venema, 1999), as follows: L Where: Lt = length of fish at age L∞ = theoretical maximum length (mm) K = growth coefficient (year) t t = age (years) Methods for determining the asymptote length (L log (-t ## 2.5. MORTALITY AND EXPLOITATION RATE2.5.1. TOTAL MORTALITY Total mortality (Z) is conducted by using the length
converted catch curve method in the FISAT II program (Pauly, 1983, Gayanilo Where: Z = total mortality (per year) 2.5.2. NATURAL MORTALITY The natural mortality rate (M) was estimated by Pauly’s equation (1983) using data on the average temperature of the Western Waters of South Sulawesi in year (T) 2017 (BMKG, 2017) with the following formula: Log (M) = -0.0066 - 0.279 Log L∞ + 0.6543 Log K + 0.4634 Log T Where: M = natural mortality rate (per year) L∞ = asymptote length of fish (mm) K = growth coefficient (year) T = average temperature of Western Water of South Sulawesi
29 2.5.3. FISHING MORTALITY Fishing Mortality Rate (F) is estimated by using the formula: Z = F + M So, it can be obtained: F = Z - M Where: F = fishing mortality (per year) Z = total mortality rate (per year) M = natural mortality (per year) 2.5.4. EXPLOITATION RATE Exploitation rate (E) is assumed by using Beverton and Holt’s equations (Sparre and Vanema, 1999) as follows: E = F / Z Where: F = fishing mortality (per year) Z = total mortality rate (per year) M = natural mortality (per year) E = exploitation rate (per year) ## 2.6. YIELD PER RECRUITMENTIt obtained by using Baverton and Holt’s equations (Sparre and Vanema, 1999), as follows: Where: M = natural mortality (per year) L’= the smallest size limit of full length of fish caught (mm) L∞ = asymptote length of fish (mm) K = growth rate coefficient (per year) E = exploitation rate (per year) ## 3. RESULTS AND DISCUSSIONTotal sample
of tuna obtained during the study was 737 consisting of 355 male tunas and 382
female tunas. The length of male tuna ranging from is 224 mm - 429 mm with the
highest frequency of length is 272 - 275 mm by 34 while the length of female
tuna ranging from 215 mm - 428 mm with the highest frequency of length is 271 -
274 mm by 34. The lengths of male tunas are classified into 52 classes and 54
female tunas with each using interval 4. ## 3.1. AGE GROUP (COHORT)Age group of tuna fish uses length frequency distribution analysis. The age group of tuna is presented in Figure 1. In Figure 1 indicates the age group of tuna (
Note: Separation index = 2 can be separated into age groups Table 1 shows that the highest number of male and female
tuna was caught in 2 Based on the separation of size groups of tuna as indicated in Table 1 that the separation index value between the size groups is more than 2. It indicates that the separation of size groups of tuna can be accepted by Bhattacharya’s method. Separation index is a relevant quantity to the study if it is possible for successful separation of two adjacent components, if the separation index < 2 then it is not possible to do separation between two size groups because of the overlap between groups of these sizes (Hasselblad, 1966; McNew & Summerfelt, 1978; Clark, 1981; Sparre & Venema, 1999). ## 3.2. VON BERTALANFFY’S GROWTH MODELThe analysis results of growth parameters in asymptote
length (L∞), growth coefficient (K), and theoretical age of fish at zero
length (t
Note: L∞ (theoretical maximum length), K (growth
coefficient, t Based on Table 2 indicates the analysis results of
parameters on male tuna, namely L∞ = 455.00 mm, K = 0.33 per year and t Based on the growth coefficient of tuna in Table 2 indicates that K in male and female tuna is smaller than 0.5. It indicated that growth in male and female tuna has slow growth. According to Sparre and Venema (1999) that the value of K < 0.5 has slow growth. Conversely, if the value of K > 0.5 has rapid growth. The estimated value of the growth parameters that have been
obtained (L∞, K and t The curve indicates that tuna will reach a theoretical maximum total length, namely in males at 455.00 and females at 453.50. It also shows that the growth rate of tuna is different each time and the growth rate of fish in the early phases of life experiences faster growth at a young age and is followed by slow growth in mature age until reaching the asymptote length where the fish do not grow anymore.
It consistent with Effendie (2002) that rapid growth occurs in fish when they are 3-5 years. In mature fish, although growth continues but it slowly. In old fish the energy obtained from food is no longer used for growth, but only used for movement, replacing damaged cells and gonad maturity. The results of Susilawati’s The difference of growth coefficient is due to differences in fishing environment and food abundance. The parameter (K) is defined as a parameter that expresses the speed of the growth curve. Therefore, the higher of coefficient of growth, the faster of fish reach its maximum length. The coefficient of growth rate (K) will affect the maximum length of fish and this is likely due to several factors namely the amount and type of food, temperature, oxygen and water quality and environmental factors so that the organisms that live in it will have different shapes and sizes (Everthart and Yuono S, 1981). ## 3.3. MORTALITY AND EXPLOITATION RATEThe analysis
results obtained the estimated values of mortality and
exploitation rate parameters of tuna in the Western Waters of South Sulawesi
can be seen in Table 3 (Appendix 3).
Where: Z (Total Mortality), M (Natural Mortality), F (Catch Mortality), E (Exploitation). Based on Table 3 shows that the male tuna has a catch mortality (F) = 0.71, natural mortality (M) = 0.41. In female fish has a catch mortality (F) = 0.87 and natural mortality (M) = 0.48. It shows that the mortality of tuna in the Western waters of South Sulawesi is more caused by fishing factors. The high of fishing mortality (F) is suspected to have an increasing number of fishing fleets each year. As the statistics of the Department of Maritime Affairs and Fisheries in Pinrang (2016), in 2014 (2.313 units), in 2015 (2.317 units), and in 2016 (2.355 units). This supports a large sizable fishing activity by fishermen every day continuously. The results of research by Fayetri
The results of Kusumawardana’s Based on the value of exploitation rate (E) of tuna found in the Western Waters of South Sulawesi, it shows that tuna has been over-exploited. As known that the maximum rate of exploitation (E) = 0.5, if it is greater than 0.5 then it is categorized as over-fishing (Gulland, 1983). The cause of the high rate of exploitation of tuna in the Western Waters of South Sulawesi is due to the ongoing fishing activities. ## 3.4. YIELD PER RECRUITMENTEstimating relative yield per recruitment (Y’/R) is one of the models commonly used as a basis for fisheries management strategies (Gulland, 1983). (Y’/R) is estimated using Beverton and Holt’s equations (Sparre and Vanema, 1999). The estimated results (Y’/R) of tuna in the Western Waters of South Sulawesi consisting of males of 0.0691 grams and in females of 0.0784 grams that can be taken part of the catch (Appendix 4) with exploitation rates exceeding 0.5. Thus, it can be said that the fishing of tuna has passed a sustainable value, and if catching is done continuously then tuna population will decrease even if it becomes extinct. Motlagh ## 4. CONCLUSIONS AND SUGGESTIONS## 4.1. CONCLUSIONBased on the results of the study can be concluded as follows: 1) Age group of male tuna has 4 cohorts and the female has 5 cohorts. 2) Asymptote
length (L∞) of male tuna can reach a size of 455.00 mm with a growth rate
of K = 0.33 per year and t 3) Mortality value in male tuna is natural mortality (M) = 0.41 and catch mortality (F) = 0.71, while mortality value for female tuna is natural mortality (M) = 0.48 and catch mortality (F) = 0.87 and the exploitation value (E) of male tuna is 0.63 per year and female tuna is 0.64. 4) Yield per recruitment relative of male tuna is 0.0691 gram and in female is 0.0784 gram. ## 4.2. SUGGESTIONSFor further research on tuna population dynamics it is recommended can be related to biological aspects, especially the level of gonad maturity, the mature size of the first gonad, spawning patterns and seasons, and the relationship of the environment and its habitat. In addition, it is necessary to observe the dynamics of tuna population for one year. So that information can be used in formulating resource management efforts to remain sustainable. ## SOURCES OF FUNDINGThis research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors. ## CONFLICT OF INTERESTThe author have declared that no competing interests exist. ## ACKNOWLEDGMENTAcknowledgments the authors
convey to all parties who have given research permission, assistance, support
and guidance to the authors including to: 1)
Regent of District and Head
of Department of Maritime Affairs/Fisheries in Pinrang
regency. 2)
Dr. Ir. St. Aisjah Fachrum, M.Sc., as the
Dean of the Faculty of Marine and Fisheries Sciences, Hasanuddin
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