FAO-ICLARM Stock Assessment Tools Research Articles

Population dynamics of the flathead grey mullet (Mugil cephalus Linnaeus 1758) in the Narmada estuary on the west coast of India

The population dynamics of flathead grey mullet, Mugil cephalus, were evaluated using length-frequency data collected from the Narmada estuary monthly between January 2018 and December 2019. The population parameters were assessed and calculated using the FiSAT-II software tool (FAO-ICLARM Stock Assessment Tools) after the estimation data were divided into 10mm class intervals. A total of 419 specimens were collected, with an average length range of 171.14±58.15mm and an average weight of 58.15±45.65g, respectively. The length-weight relationships were established as W = 0.0105 L2.979. Length-frequency data revealed that length groups 140-149 (15.75%) and 130-139mm (13.37%) dominated the commercial catches of M. cephalus at the Narmada estuary. Different growth parameters were estimated as L∞ = 309.75mm, K = 0.41yr-1 and t0 = -0.0013 years. The estimated values of mortality coefficients Z, M, and F were 1.06yr-1, 0.52yr-1 and 0.54yr-1, respectively. The value of exploitation ratio (E) by using the length-converted catch curve method was established as 0.51, which was found to be a little high from the optimum value (0.50). The recruitment was found to be continuous almost throughout the year, with two peaks, once during February to May and another during August to October. The maximum sustainable yield (MSY) was estimated at 970.218 t if the suggested length at first capture (Lc = 123.44mm TL) is maintained throughout the capture periods. The fishing pressure was found to be slightly excessive for the current stocks, which should be considered for proper management of the fishery in the Narmada estuary.

Population Dynamics of Mangrove Clam Pegophysema philippiana (Reeve, 1850) in Davao Region, Southeastern Mindanao, Philippines

Mangrove clam is the most sought-after bivalve in the Philippines due to its taste, size, and nutrition. Due to its economic importance, this paper aims to determine the population dynamics of mangrove clam P. philippiana harvested in gleaning sites in the Davao region using the FAO ICLARM Stock Assessment Tool (FISAT II). A total of 2493 clams collected from December 2018-December 2020 with sizes ranging from 14-84 mm SL and 2.2-178.6 g were classified according to size classes with 5 mm intervals. The length-weight relationship was computed and showed negative allometry (a = 0.002, b = 2.6205, R2 = 0.89). The estimated growth parameters using ELEFAN I was L∞ = 98.64 mm, K = 1.33 year-1, t0 = -1.07. Length converted catch curve routine estimated Z = 10.27year-1, M = 1.52 year-1, F = 8.75 year-1, E = 0.85, and backward extrapolation generated Lc50 = 34.83 mm SL which is below Lm = 65.76 mm SL. Recruitment patterns were highest during July and August 2020, and VPA showed a high F at 60 mm SL. Beverton and Holt Y/R analysis showed E0.5 = 0.328 and Emax = 0.551, yield isopleths derived from plotted Lc50/L∞ = 0.353 and E = 0.85 values were within quadrant D. The result revealed that Lm>Lc50 implies that mangrove clams gleaned in the area were small and immature. Moreover, F>Fopt and E>Emax and E>E0.5 suggest that mangrove clam fishery in the region was heavily exploited. The study concluded that the mangrove clam Pegophysema philippiana was overexploited and that a management strategy was needed in the Davao Region, Philippines.

Age, Growth, and Mortality of Pontic Shad, Alosa immaculata Bennett, 1835, in the Danube River, Romania

This study aimed to evaluate the growth, mortality parameters, and exploitation rate of Pontic shad, Alosa immaculata Benett, 1835, in the Danube River, Romania (km 169–197). The sampling collection started with the first signs of Pontic shad migration, on 4 March 2023, and continued weekly until the beginning of June 2023, when the last specimens were caught in the nets. The estimation of the growth, mortality parameters, and exploitation rate was done in FiSAT (FAO-ICLARM Stock Assessment Tools). The von Bertalanffy growth equation was estimated at L∞ = 36.75 cm, the growth coefficient was k = 0.68 year−1, and the theoretical initial age was t0 = −0.67 year−1. The total mortality rate (Z) estimated was 2.76 year−1, with a natural mortality rate (M) and fishing mortality rate (F) of 0.89 year−1 and 1.87 year−1, respectively. The Z/k ratio was found to be 4.11 and the exploitation rate (E) was estimated at 0.68 year−1, indicating the overexploitation of Alosa immaculata stocks. In conclusion, this study provides valuable insights into the population dynamics of Pontic shad in the Danube River, Romania. The assessments of the growth parameters, mortality rates, and exploitation rates highlight a level of overexploitation of Alosa immaculata stocks. These findings underscore the importance of applying effective fishery management strategies to ensure the sustainability and conservation of this valuable fish species in the Danube River ecosystem.

Estimating the growth parameters, exploitation rate, biomass and maximum sustainable yield of long whisker catfish Mystus gulio (Hamilton, 1822) in the coastal waters from southwestern Bangladesh

The research provides a comprehensive analysis of Mystus gulio including growth pattern, growth parameters, recruitment patterns, mortality rates, biomass, exploitation rate (E), and the estimation of maximum sustainable yield (MSY) within the southwestern coastal waters of Bangladesh. From January to December 2017, fishers provided around 1200 specimens. FAO-ICLARM Stock Assessment Tool and Excel-add-in-solver were used to assess stock status through length-frequency data. Indeed, the research findings indicated that the population of M. gulio displayed negative allometric for both individuals (b = 2.53 for male, b = 2.50 for female), as demonstrated by the calculated allometric coefficient value. Nonetheless, the population's dynamic characteristics revealed an asymptotic length (L∞) of 19.34 cm, 23.28 cm and growth coefficient (K) 0.94 year−1 and 0.81 year−1 for male and female M. gulio. The growth performance indexes (Ø') of 2.55 and 2.64 for male and female and maximum lifespan (tmax) 3.20 years and 3.70 years respectively. This study revealed that the slightly variations in the natural mortality rate (M) for both specimens at 1.55 year−1 and 1.59 year−1. The fishing mortality rate (F) 2.75 year−1 and 1.98 year−1and total mortality rate (Z) 4.30 year−1 and 3.57 year−1 for male and females, respectively. The maximum permissible exploitation rate (Emax = 0.421) was lower than the actual exploitation rate (E = 0.63). The MSY was calculated at 67.968 metric tons. Without a doubt, overfishing stands out as the most critical threat to the wild stock. Therefore, it is clear that the existing fishing approach was not efficiently managed the standing stock in a sustainable manner. The findings would be useful for established proper fishing regulations in coastal waters and the surrounding ecosystems.

POPULATION PARAMETERS OF BLUE SWIMMING CRAB PORTUNUS PELAGICUS IN THE TIWORO STRAIT, SOUTHEAST SULAWESI

The blue swimming crab (Portunus pelagicus) has a wide distribution in the fishing ground waters for fishermen's activity in the Tiworo Strait. The coastal area of Tiworo Strait has quite a lot of crab potential. Therefore, it is used as one of the pilot locations for sustainable crab management projects of the Indonesian Blue Swimming Crab Association (APRI). Growth, total mortality, natural death, fishing mortality, and the exploitation rate were the population parameters of crabs that need to be known so that management can be carried out in a sustainable manner of fisheries. A study on the population parameters of crabs has been conducted in the Tiworo Strait, based on carapace width frequencies data collected from Juli to December 2021 and analyzed using FISAT (FAO-Iclarm Stock Assessment Tool) II. The total sample is 7,809 samples, where the number of male blue swimming crabs is 3,295 samples and 4,514 females. The average size of the blue swimming crab carapace width caught was 107.57 mm for males and 110.65 mm for females. The results of the study showed that the growth rate (K) was 1.01/year, the total mortality rate (Z) was 0.67/year, the natural death rate (M) was 1.25/year, and the fishing mortality rate was 0.58/year. The exploitation rate (E) of blue swimming crab was 0.86, which showed symptoms of over–exploitation, so the management of crabs in these waters must be carried out more carefully to sustain the availability of crab resource stocks. 
 Keywords: blue swimming crab, width, weight, Tiworo Strait

Population dynamics of thresher shark (Alopias pelagicus) landed at the Kutaraja fishing port, Banda Aceh

At the Kutaraja Fishing Port, the shark species Alopias pelagicus accounts for the vast majority of shark catches. The purpose of this research was to ascertain the length distribution of A. pelagicus, the length at which it was first captured, the sex ratio, the von Bertalanffy growth parameters and functions, the mortality rate, and the exploitation rate. This study was carried out in the Kutaraja Fishing Port from December 2021 to February 2022. The incidental sampling method was used to collect 406 samples in total. The FAO-ICLARM Stock Assessment Tools were utilized to analyze population dynamics parameters. The male, female, and combined length distributions of A. pelagicus ranged from 186-295cmTL, 205-304cmTL, and 186-305cmTL, respectively. The length of the first capture was 249.40 cmTL, 252.29 cmTL and 250.78 cmTL, sex ratio of males and females is 1:2.24, the asymptotic length (L∞) was 344.25 cmTL, fish age at length 0 (t0) was 0.066/year, with a growth rate (k) of 0.50/year, 0.36/year dan 0.19/year, 374.83 cmTL and 378.92 cmTL, 0.058/year dan 0.048/year. Natural mortality (M) was assessed to be 0.59/year, 0.47/year, and 0.31/year, fishing mortality (F) was 2.08/year, 2.47/year, and 2.20/year, and total mortality (Z) was 2.67/year, 2.94/year, and 2.51/year. The A. pelagicus exploitation rate (E) was 0.78/year, 0.84/year, and 0.88/year, demonstrating complete exploitation of the male, female, and combined populations.

Pertumbuhan Ikan Tongkol Abu-Abu (Thunnus tonggol Bleeker, 1851) yang Tertangkap di Perairan Selat Bali

Longtail Tuna (Thunnus tonggol) in the waters of the Bali Strait is a by-catch fish, so that information on this fish resource was still very lacking and its management of longtail tuna was often neglected. The aimed of this study is to predict the signs of the unsustainability of longtail tuna resources based on growth aspects which include the distribution of length frequency, estimation of age groups, growth patterns and growth parameters. Data collection was carried out from December 2018 to February 2019. The growth pattern estimated by relationship of length and weight, cohort was identified using an analytical model based on the FISAT program (FAO I-CLARM Stock Assessment Tools) and growth parameters were analyzed using the Von Bertalanffy growth model. It can be seen that, the catch is dominated by the size of the fish that have matured gonads or adults (69% females and 73% males). The growth pattern of female and male of longtail tuna is negative allometric (length growth is more dominant than weight). So it can be assumed that there is an inconvenience in environmental conditions and competition in fighting for food and space in the waters of the Bali Strait.Longtail tuna had asymptotic length values of 784.71 mm (female) and 738.04 mm (male) with growth coefficients of 0.13 (female) and 0.18 (male). The growth performance inteprated as quite high when compared to other waters in Indonesia.

Length/weight relationships and condition factor of Trachinotus goreensis from Bonny Estuary, Nigeria

The length-weight relationships and condition factor of golden pompano (Trachinotus goreensis) from Bonny Estuary, Rivers State, Nigeria, was studied for a period of three months (January – March, 2021). Fish samples were collected from local fishers at the landing sites in the estuary. A total of 246 samples of T. goreensis with total lengths ranging from 18.00 -70.00cm and a corresponding weight range of between 470.00- and 3000.00g were recorded. Samples were identified using standard fish identification keys. Length – weight relationships and condition factor were calculated according to standard methods. Data were subjected to FAO ICLARM Stock Assessment Tools (FISAT II) and Microsoft Excel for regression analysis. The mean intercept constant (a) obtained for T. goreensis was 0.39. The slope (b) value was 2.33, showing a negative allometric growth pattern. The correlation coefficient (r) value for the species was 0.94 indicating a positive relationship between the length and weight. The overall monthly condition factor (K) of the species was 1.56 indicating that the fish was in good condition. It could be inferred that T. goreensis from Bonny Estuary had negative allometric growth and was found to be doing well judging from its condition factor.
 Keywords: Growth, Allometry, Trachinotus, Condition factor, Estuary

Stock Assessment of the Blue Swimming Crab Portunus pelagicus (Linnaeus, 1758) in Stock Enhancement Sites of Danajon Bank, Central Philippines

The stock status of Blue Swimming Crab (BSC), Portunus pelagicus, locally known as lambay, in Danajon Bank was assessed from June 2019 to September 2020 to monitor the impact of the BSC stock enhancement initiative by the Philippine Association of Crab Processors, Inc. (PACPI) in collaboration with BFAR 7. The stock was assessed based on the indicators, namely, catch per unit effort (CPUE), exploitation rate (E), average size, length at first maturity (Lm), and Spawning Potential Ratio (SPR). Data analysis was done using FAO-ICLARM Stock Assessment Tools (FiSAT) II software and the Barefoot Ecologist’s Toolbox for the Length-based Spawning Potential Ratio (SPR). Results show that BSC dominated the monitored landings accounting for 66% of the overall catch harvested mainly by crab pot and crab net. Higher CPUEs were obtained in the months of July, June, May and August with annual mean observed to be higher than the previous assessment conducted by ECOFISH in Danajon Bank particularly for crab pot. Population characteristics revealed that male crab grew slightly faster having higher asymptotic length (L∞ =21.65cm Carapace Width or CW) and growth constant (K=1.3yr-1) than female (L∞ =21.40cm CW, K=1.28yr-1). Sex ratio of male to female was at 1:1.28 indicating plenty of female crabs were captured than male. Gravid crabs were abundant in May, December, April and October. Recruitment pattern showed two pulses with primary peak occurred in April and May and secondary pulse happened in August and September. Encouraging performance indicator noted from this assessment was on the bigger probability of capture sizes and mean length of commonly caught BSC falling above the recommended catchable size of 10.2 cm CW pursuant to DA-DILG JAO No. 1 s. 2014. Maturity size (Lm) was estimated at 10.54 cm CW, though smaller than the previous reported Lm values in Danajon but still within the threshold. The estimated SPR was 26%, higher than 20% limit reference point but slightly lower than 27% recorded in the assessment done by ECOFISH Project in 2014 to 2015. The present SPR though lower than 30% precautionary threshold however higher than 21% generated in Visayan Sea Region 7 for the same period. The higher SPR in Danajon Bank compared to Visayan Sea maybe credited to the effect of stock enhancement activity implemented in the area, though observation is not yet conclusive. On the other hand, unfavorable indicators were seen on high exploitation rate (E), high exploitation at yield per recruit some of which already breached the optimum level, consequently subjecting Danajon Bank to high fishing pressure. It is recommended to continue the BSC stock enhancement program of PACPI and BFAR 7 taking consideration some strategies for improvement specified in the recommendations.

Population parameters of several groupers (Famili Serranidae) in Labuan Bajo waters, East Nusa Tenggara

Labuan Bajo has a fertile aquatic ecosystem, one of them is the coral reef ecosystem. This condition happened because of the supply of nutrients that are carried through Indonesia Through Flow and the local upwelling phenomena. Various species of reef fish of various sizes have been caught in Labuan Bajo waters. In general, the type of reef fish that dominates is grouper fish catch by using handline fishing gear. Furthermore, there is damage that occurs in the coastal ecosystem causes changes in ecological functions and disrupted ecosystem benefits. In addition, pressure from overuse did not provide opportunities for resources to carry out recovery makes the condition of resource stocks threatened. This study aims to determine the parameter aspects of the population of several types of grouper fish in Labuan Bajo waters. The types of grouper studied included Plectropomus leopardus, P. maculatus, P. oligacanthus, and Variola albimarginata. Data collection was carried out by enumerators from April to August 2019 which included the daily data on the length and weight distribution of groupers. Length-frequency distribution data is analyzed by estimating fish population parameters using the Electronic Length Frequency Analysis (ELEFAN I) program which is packaged in the FAO-ICLARM Stock Assessment Tool II (FiSAT II) software. The results of the analysis showed the equation of growth parameters for Von Bartalanffy for P. leopardus is Lt = 89.06(1-e−0.24(t+0.52)); P. maculatus is Lt = 76(1-e−0.54(t+0.23)); P. oligacanthus is Lt = 72.32(1-e−0.66(t+0.19)); and V. albimarginata is Lt = 45(1-e−0.51(t+0.29)). The length at first birth of each species is Lt=0 P. leopardus = 10.45 cm, Lt=0 P. maculatus = 8.88 cm, Lt=0 P. oligacanthus = 8.52 cm, and Lt=0 V. albimarginata = 6.19 cm. Meanwhile, the exploitation rate (E) of P. leopardus, P. maculatus, P. oligacanthus, and V. albimarginata were 0.81; 0.53; 0.45; and 0.70.

Evaluating the Effects Related to Restocking and Stock Replenishment of Penaeus penicillatus in the Xiamen Bay, China

The quantitative evaluation of restocking and stock replenishment is essential for providing operational feedback and implementing adaptive management for future restoration projects. Since 2010, approximately 700 million juvenile shrimp (Penaeus penicillatus) have been released into Xiamen Bay, Fujian Province, China, each year, through stock replenishment programs. The recruited shrimp were sampled through three-year bottom trawl surveys from 2014 to 2017. The biological characteristics and catch equation were used to evaluate the effect of restocking and stock replenishment. The analysis uses the FAO-ICLARM Stock Assessment Tool (FISAT II) program. In general, there are two sources of recruitments—one from spawning brood stock and the other from released juvenile shrimp. We constructed an evaluation model for an effect evaluation based on Baranov’s catch equation to separate the initial recruitment volume using survey data. The relationship between body weight and total length was W = 1.638 TL2.9307. There is no statistically significant difference between males and females. The von Bertalanffy growth parameters derived for prawns, using FiSAT II, were L∞ = 209.6 mm and K = 0.51 per year. In spring 2014, the initial resource amount was 49,200, while the ratio of effective recruitment and parent amount was 3.92. The survival rate of the released shrimp larvae, 1.88‱, seems to be very unsatisfactory. The resource amount in summer and autumn is higher than in winter and spring. Obviously, the restocking effect is lower and the programs need to be improved. To improve the restocking effect, the replenishment performance should be adjusted to reduce the mortality rate and increase its release effectiveness. Therefore, corresponding implementations are recommended, including standard extensive culture, reduction in stress during transportation, and temporary culture.

Stock assessment of Hooghly Croaker Panna heterolepis in the Bay of Bengal (Southern Bangladesh): implications for sustainable management

The study describes growth pattern, growth parameter, mortality, recruitment pattern, exploitation rate (E) and maximum sustainable yield (MSY) to Panna heterolepis from the Bay of Bengal (Bangladesh). About 1223 specimens were collected from commercial fishermen for 12 consecutive months from January to December, 2019. Length–frequency data were analyzed with FAO-ICLARM Stock Assessment Tool. Moreover, our study recorded different water quality and environmental parameters including pH, rainfall, temperature and DO (dissolved oxygen) from the Bay of Bengal. The findings of the study revealed that the allometric co-efficient (b) value indicated negative allometric growth (<3.00) for P. heterolepis population. Whereas, the population dynamic parameters showed growth coefficient (K) 0.13 year−1, life-span (tmax) 3.85 year and growth performance index (Ø′) 2.30. Along with this, P. heterolepis was found to grow rapidly with an asymptotic length (L∞) of 39.08 cm. We found that the natural mortality (M =0.44 year−1) rate was almost similar with fishing mortality (F = 0.42 year−1). Consequently, the standing stock was not quite sustainable with the existing fishing strategy. Furthermore, the maximum allowable exploitation rate (Emax= 0.471) was lower than the recorded exploitation rate (E = 0.490). Subsequently, overfishing is the most focal threat to the wild stock. The recruitment pattern was almost continuous throughout sampling period. Finally, the MSY was assessed at 10234.47 metric tons. Additionally, the environmental parameters denoted that the ecosystem was in a balanced condition for the wild population. The findings would be very useful to introduce appropriate fishing regulations in the Bay of Bengal and nearby ecosystem.

Population dynamics of Chrysichthys nigrodigitatus (Lacépède, 1803) in Ikere-gorge, Oyo State, Nigeria

The growth and mortality parameters of Chrysichthys nigrodigitatus were estimated to assess the sustainability of its exploitation in Ikere-gorge, Oyo State, Nigeria. A total of 1210 of Chrys­ichthys nigrodigitatus were sampled from fishermen catches between January, 2017 and Decem­ber, 2018. C. nigrodigitatus were exploited with gillnet, cast net and traps (Malian trap net and bamboo). Total lengths were measured with fish measuring board. The FAO-ICLARM Stock Assessment Tool (FiSAT II) software was used to analyze length-frequency data of the fish. The estimated growth parameters are: asymptotic length is 60.9 cm, growth coefficient is 0.96, optimum length is 38.51 cm; length at maturity is 33.44 cm while length-at-first-capture is 12.62 cm. The estimated mortality parameters are: total mortality is 3.29 per year, natural mortality is 1.43 per year and fishing mortality is 1.86. It was observed that C. nigrodigitatus of Ikere-gorge were more vulnerable to exploitation at sizes less than their length at maturity. Likewise, the ex­ploitation rate (E = 0.57 yr-1) is greater than sustainable exploitation rate (Emax = 0.46 yr-1). This shows that exploitation of C. nigrodigitatus in Ikere-gorge is not sustainable. Therefore, there is need to reduce fishing pressure on C. nigrodigitatus to ensure its sustainability in Ikere-gorge.

Growth, mortality, recruitment pattern, and exploitation rate of shared stock flying fish (Exocoetidae) at border area of Indonesia and Timor Leste in Ombai Strait

Flying fish (Exocoetidae) is one important small pelagic fisheries commodity in border areas of Indonesia and Timor Leste. However, the data of population parameters in Ombai Strait are not yet known, which is important to inform unit stock management and sustainable fisheries. This study aimed to provide information about growth and mortality parameters, recruitment pattern, and exploitation rate of flying fish. Data collection was carried out during May 2018-June 2019 by measuring and observing the flying fish landed at the fish landing sites in Belu Indonesia and Bobonaro Timor Leste. Data analysis used the FAO-ICLARM Stock Assessment Tools (FiSAT) program. The results showed that the asymptotic length (L∞) was 330.5 mm, growth constant (K) was 0.99 per year, and growth performance indices (Φ) was 0.50. The natural mortality (M) was 0.92 per year, fishing mortality (F) was 0.12 per year, and total mortality (Z) was 1.04 per year. The highest recruitment occurs in May to September with peak season in June (14.82%) and September (15.16%). Exploitation rate (E) flying fish in the border area of Indonesia and Timor Leste in Ombai Strait is relatively low about 0.11 and still at a rational and sustainable utilization range (E < 0.5).

Population dynamics of Indian scad (Decapterus russelli) in the northern and western waters of Aceh

Indian scad (Decapterus russelli) is an important commercial species that landed at the Fishing Port of Kutaradja, Banda Aceh. This research was conducted to investigate the impact of exploitation on D. russelli stock based on length-weight relationship, length distribution, length at first capture, von Bertalanffy growth parameters and function, mortality parameters, and exploitation rate. The data collection was conducted from February to March 2020 in the Fishing Port of Kutaradja, Lampulo, Banda Aceh. A total of 170 samples were measured with stratified random sampling method. Analysis of population dynamics parameters used the FAO-ICLARM Stock Assessment Tools (FiSAT) program. The results show that D. russelli has a positive allometric growth pattern, with a fork length (FL) ranging from 19.5-31.5 cm. The length of first capture was 23.1 cm. The asymptotic length (L∞) of D. russelli was 31.50 cm with a growth rate (k) of 0.88/year and fish age at length 0 (t 0 ) of 0.178/year. The estimated natural mortality (M), fishing mortality (F), and total mortality (Z) were 1.63/year, 2.22/year and 3.85/year respectively. The exploitation rate (E) of D. russelli was 0.58/year that indicated D. russelli in the northern and western waters of Aceh has been fully exploited.

Population dynamics of skipjack tuna (Katsuwonus pelamis) in the northern and western waters of Aceh

Skipjack tuna (Katsuwonus pelamis) is a pelagic fish species that have important economic value in the northern and western waters of Aceh. Skipjack tuna is one of the dominant catch fish landed at the Fishing Port of Kutaraja, Banda Aceh. The dynamics population of skipjack tuna in the northern and western waters of Aceh need to be done to get information on the status of skipjack tuna in ocean. This research aims to determine the dynamic parameters of the population of skipjack tuna based on the growth parameters, length and weight relationship, length distribution, length at the first capture, mortality, and exploitation rate. The data collection was conducted in February to March 2020, located at the Fishing Port of Kutaraja, Lampulo, Banda Aceh. A total of 166 sample, were measured with stratified random sampling method. The FAO-ICLARM Stock Assessment Tools (FiSAT) program was used by analyze growth parameter, mortality parameters, and exploitation rate. The results showed that has a negative allometric growth pattern, with a length of fork length (FL) ranging from 25-51 cm. The length of first capture was 38,2 cm. The asymptotic length (L∞) of skipjack tuna was 84,78 cm with K value of 0.22/year and. The estimated natural mortality (M), fishing mortality (F), and total mortality (Z) were 0,5/year, 1.55/year, and 2.99/year respectively. The exploitation rate (E) of skipjack tuna was 0.83/year that indicated skipjack tuna in the Northern and Western waters of Aceh over-exploited.

Demographics of Butterfly Fish, Heniochus acuminatus (Perciformes, Chaetodontidae) from the Gulf of Mannar, India

Butterfly fishes are widely distributed throughout the Indo-Pacific Ocean and are often caught in large quantity by shrimp trawlers as a by-catch species. These fish are ecologically and commercially important, as they are ecological indicators of coral health and a major component of ornamental and by-product fisheries. However, owing to their low value for direct human consumption as a food, there is dearth of research on their demographics and life–history traits. The present study was therefore conducted using Heniochus acuminatus, one of the common butterfly fish that is captured as a by-catch in the Gulf of Mannar (GoM) to generate basic data on its demographic estimates. Specimens (n = 833) were collected monthly from the four reef-fish landing stations for two consecutive years and the demographic parameters were estimated using a FAO–ICLARM Stock Assessment Tool (FiSAT). Fish in the length class of 10–11 cm dominated the landings. The length-weight relationship (LWR) was defined as the equation, BW = 0.0234TL3.156 suggesting positive allometric growth pattern of H. acuminatus in GoM. Estimated demographic parameters (asymptotic length, L∞ = 17.85 cm) showed low growth rate and growth performance index (K = 0.95 and ϕ = 2.481 respectively) in study species. The estimated potential longevity (tmax) and the observed length at first capture (Lc) were found to be 3.15 years and 7.9 cm respectively. The higher natural mortality rate (M = 2.00 yr−1) than the fishing mortality rate (F = 0.39 yr−1) with exploitation level (E = 0.16) below the optimum level indicates that the state of the stock of H. acuminatus in the GoM is sustainable. The current study provides the first population demographic report of the genus Heniochus and is likely to have a significant conservation and commercial impact.

Stock Assessment of Parrotfishes “Molmol” (Sub-Family Scarinae, Family Labridae) in the Major Fishing Grounds of Bohol, Central Visayas

The issue on the overfishing of parrotfishes, locally known as “molmol” (subfamily Scarinae under family Labridae), in the coastal waters of Bohol province in Central Visayas has been raised by the Provincial Agricultural and Fishery Council (PAFC) of Bohol through Resolution No. 1 series of 2018 that pushes for the implementation of “open and closed fishing season” of all parrotfishes in the entire province. In any management intervention, baseline assessment of the stocks in question should be done as a significant basis for appropriate measures to be taken, thus this study. In Bohol, apart from the economic value, they carry essential functions in maintaining the ecological balance in the reef ecosystem. Parrotfishes are considered economically important as preferred fish among locals and tourists. The stock assessment of parrotfishes in Danajon Bank in the Bohol Sea and Cebu Strait was conducted by the National Stock Assessment Program (NSAP) Region 7 from 2015 to 2018 in 16 coastal municipalities of Bohol. It recorded 24 Scarine species across six genera. The green humphead parrotfish (Bolbometopon muricatum), categorized as vulnerable under the International Union for Conservation of Nature (IUCN) red list, was noted in Cebu Strait in 2015. Scarus ghobban, comprising 82.25%, dominated the catch in Danajon Bank; Scarus forsteni (30.07%) in Bohol Sea; and Chlorurus sordidus (58.45%) in Cebu Strait. Among the Scarines, S. ghobban dominated across fishing grounds from 2015 to 2018 with an aggregate of 10,267.69 kg (or 63.94%) monitored catch equivalent to 0.26% relative to all other species surveyed in the same period. The assessment also indicated that among the 22 fishing gear types being observed as used in catching parrotfishes, speargun is the most prevalent or frequently used. Moreover, the same assessment showed that the catch seasonality of S. ghobban determined from spear gun appears to be abundant during the first quarter in a year; in June, August, and December when higher monthly mean Catch per Unit Effort (CPUE) were also noted. However, the annual mean CPUE of speargun has decreased from 11.93 kg/day in 2017 to 9.22 kg/day in 2018. Population parameters of S. ghobban as the top one species were estimated using the FAO-ICLARM Stock Assessment Tools (FISAT) software and Froese Indicator Tool. Biological indicators for S. ghobban show signs of overfishing as reflected on its high fishing mortality (F/M), decreasing average length below maturity length, decreasing catch per unit effort in the current year, low percentage of mature in the catch, and increasing exploitation ratio (E). All of which already breached the limit reference points. In 2017 and 2018, the mature size composition of the catch was only 1.9 percent and 0.3 percent, respectively, far off from the 90-100% target and below the 50% limit. The values indicate that majority of the samples were small sizes; however, it cannot be determined if they were juveniles since this study excludes reproductive sampling. Optimum length (Lopt) was estimated at 29 cm (Total Length); lengths within ± 10% Lopt range at 26.1 to 31.9 cm and megaspawner at 31.9 cm up. Based on the results, suggested recommendations are indicated herein for possible consideration of the policymakers.

Growth, Mortality and Yield-per-recruit of Nile Tilapia (&lt;em&gt;Oreochromis niloticusM/em&gt;) in Garmat Ali River, Iraq

The study was conducted to estimate the growth, mortality, recruitment and yield-per-recruit of Oreochromis niloticus from Garmat Ali River, Basrah, Iraq from October 2019 to September 2020. The population parameters were analyzed using the FAO-ICLARM stock assessment tool (FiSAT). A total of 2696 O. niloticus ranged from 7.0 to 25.0 cm and the sizes 13.0-18.0 cm constituted 64.2% of the total catch. The length-weight relationship was W= 0.012L3.109 suggesting that the species shows positive allometric growth. The growth parameters for the species were estimated as L∞= 30.45 cm, K= 0.45, to= -0.313 and Ǿ= 2.622. The coefficients of total mortality (Z), natural mortality (M) and fishing mortality (F) were 3.26, 1.03 and 2.24, respectively. The exploitation rate for the species computed to be 0.69. Fish were recruited to the fishery at a mean size of L50= 14.92 cm. The peak of recruitment was 23.51% in June. The analysis of yield-per-recruit (Y/R’) indicates that stock is not being overfished since the present exploitation rate was below the biological target reference points (E0.1 and Emax). So, more yields could be achieved by reducing the mesh sizes of the nets for fishing the species

Growth, mortality and exploitation rate of Indo-Pacific King Mackerel (Scomberomorus guttatus, Bloch and Schneider, 1801) in the Tarakan waters, North Kalimantan, Indonesia

Indo-Pasific King Mackerel or fisherman in Tarakan often call it the mackerel (Scomberomorus guttatus, Bloch & Scheneider, 1801) was the main catch of gillnet fishermen in the waters of Tarakan, North Kalimantan. This research aims to obtain data and information about the estimated rate of growth, mortality rate and exploitation rate. Time series data was collected from the fishing place in Selumit, Tarakan from April to December 2018. Parameter estimation was done using the FISAT II (FAO-ICLARM Stock Assessment Tools) program. The results of the study showed fork length of mackerel between 23-61 cmFL, each month mode varying between 29 – 39 cmFL with an average mode of 35 cmFL, growth patterns were negative allometric, The average length at first capture (Lc) smaller than the length at first maturity (Lm) so if this condition continue it will interfere the sustainability of fish resources. The growth rate (K) amounted to 0.28 per year with an asimptotic length of 64.21 cm. The total mortality rate (Z) of 1.44 per year, with a natural mortality rate of 0.64 per year, the rate of fishing mortality (F) amounted to 0.80 per year. The exploitation rate (E) of 0.56 per year indicates that the degree of harvesting leads to a more capture condition.