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The Kayan River is the longest in North Kalimantan, inhabited by various types of aquatic biota. However, in recent times there have been established multi-national oil palm plantations and mining around the Kayan River which will have an impact on the Kayan River ecosystem. The aim of this study is to determine the ecological status of the Kayan River based on current conditions. Fish sampling is carried out along the Kayan River starting from the upper reaches of the Bahau River to the downstream. Identification of fish is based on the Fishbase Organization, FAO and Kottelat. Measurement of water discharge using the SNI 8066: 2015 method, Total Suspended Solid refers to SNI 06-6989.3-2004. Determination of species diversity using the Shannon-Wiener Index, while the measurement of dominance index uses the Simson Index. The results obtained 37 species from 16 families during the 2019-2020. The family of Cyprinidae is the largest fund with 32%. Among the 37 species found 9 native species of Kalimantan, 3 invasive species, 1 species of saltwater fish, and 2 species of fish are included in the IUCN red list. Fish that are included in the endemic/native category of the Kayan River are Anguilla borneensis, Hemibagrus capitulum, Nematabramis alettes borneensis, Clupeoides borneensis and Osphrenemus septemfaciatus, and Pangasius rheophilus. Based on the results of the study, it can be concluded that the ecological status of the Kayan River fish is still considered very good and stable during the research period.

Highlight The sex ratio of giant prawns in the waters of fe- male groceries is 3 times higher than that of males. The growth characteristic of male and female giant prawns is negative allometry, but the male and female body shapes are fat. Total mortality, capture mortality, catch rate, male prawns are higher than females. The male infinitive growth is longer than the female,but the female’s growth rate is faster than male. Abstract Giant prawns ( Macrobrachium rosenbergii ) is a crustacean class that has the larg- est size and its habitat in Sembakung waters included brackish water (estuarine) with a salinity variable of 6.5 + 0.5 ppt and a temperature variable of 28.5 + 0.5OC and a variable pH of 6 (acidic). The objective of this research was to analyze the growth and mortality model of giant prawns ( M. rosenbergii ) that was taken from the catch of fisherman in the estuary, Sembakung sub-district, Nunukan Regency, Indonesia. The study was conducted for 3 months from November 2019 to Janu- ary 2020. The sampling was by using a survey method with purposive judgment sampling based on a catch of 14 fishermen who used the bottom fish pot from Sembakung waters, Nunukan Regency (Indonesia). The data collection included data of sex, total length, and the total weight of giant prawns. While analysis was employed for growth pattern, condition index, Von Bertalanffy growth, and mor- tality. The results obtain the sex ratio of male and female giant prawns 1:3.67. The growth pattern of male and female giant prawns were allometric negative. The growth of the von Bertalanffy model for infinitive growth of male giant prawns were 21.219 cm and female were 18.42 cm, respectively the mortality from giant prawns obtain total male mortality is 2,257, catch mortality is 1.92 and natural mortality is 33.75% with an exploitation rate of 0.85 (85%). The total female mor- tality is 1.528, catch mortality is 120.1% and natural mortality is 32.69% with an exploitation rate of 0.786 (78.6%).

Salim G, Handayani KR, Anggoro S, Indarjo A, Syakti AD, Ibrahim AJ, Ransangan J, Prakoso LY. 2020. Morphometric analysis of Harpodon nehereus, Harpiosquilla raphidea, and Scylla serrata in the coastal waters of Tarakan, North Kalimantan, Indonesia. Biodiversitas 21: 4829-4838. The Bombay duck (Harpodon nehereus), harpiosquillid mantis shrimp (Harpiosquilla raphidea), and giant mud crab (Scylla serrata) are among the commercially important fishery resources in Tarakan Island, North Kalimantan, Indonesia. This requires sustainable fisheries management to be in place since these resources have now become the main targets of fishing industry. However, sustainable fisheries management of these species is difficult because less is known about the species particularly its condition, fatness, and well-being. Hence, the current study was conducted to analyze the morphometric characteristics in order to deduce fishing pressure of the fish species in Tarakan waters. Data collection was achieved through field between September 2017 and April 2018. Morphometric characteristics (length, weight, width, and thickness) were collected throughout the sampling period. The length-weight relationship and condition factor were then estimated using the morphometric measurements. The data were then statistically analyzed either or combination of t-test, Chi-square, and the Mann-Whitney tests. The study revealed that all the three fish species (H. nehereus, Ha. raphidea, and S. serrata) populations in Tarakan waters were dominated by male individuals (M:F ratio; 1:0.81; 1:0.63; and 1:0.66, respectively). The length-weight analysis showed all fish were found to be smaller in size and exhibited negative allometric growth patterns. The analysis of condition factor also showed that the fish were dominated by flat and very flat body shapes. The current study suggests that the fish species may encounter some kinds of ecological disturbances that selectively removed female fish and larger individuals from the populations. However, more studies are needed to accurately identify those factors so that plans to effectively address the root cause could be incorporated in the sustainable fishery management tools of the fish resources.

In order to clarify the influence of the interposition of pink muscle fiber into the dorsal ordinary muscle on the post-mortem temporal change of K-value, using carp (cultured) Cyprinus carpio, the dorsal muscle was divided into five muscle parts toward depth with the naked eye, as follows: the dark muscle part (P-1), the intermediate muscle part (P-2), and three ordinary muscle parts (P-3, P-4, P-5). The muscle fiber types in these parts were discriminated by the inactivation of actomyosin ATPase activity for both acid and alkaline preincubations, and the temporal changes of ATP related compounds in these parts were then measured at a kept temperature of 32℃. Five muscle parts were organized from the muscle fiber types as follows: P-1 was organized from only red muscle fiber type, P-2 from only pink muscle fiber type in a thin layer and from two muscle fiber types of not only pink muscle fiber, but also white muscle fiber of the Ⅱa or Ⅱb subtype in a region of mosaic pattern, and all of P-3, P-4, and P-5 were from two muscle fiber types of white muscle fiber (Ⅱa or Ⅱb subtype) and pink muscle fiber, respectively. The temporal changes of K-value were remarkably faster in order of the dark muscle part of P-1, the intermediate muscle part of P-2, three ordinary muscle parts of P-3, P-4, and P-5, although its change did not exhibit a remarkable difference among three ordinary muscle parts. On the other hand, the temporal change of K-value among muscle fiber types was considerably different and remarkably faster in the order of: red muscle fiber, pink muscle fiber, and white muscle fiber. From these results, it was considered that the interposition of pink muscle fiber into the dorsal ordinary muscle might accelerate the temporal change of K-value., 長崎大学水産学部研究報告 v.83 p.5-12 , 2002

The difference in interposition ratio of pink muscle fiber among various fish species was studied to learn its influence in dorsal ordinary muscle on the post-mortem change of K-value. A remarkable mosaic pattern was exhibited in the interpositioned white and pink muscle fibers in many of the species. The relative number and area percentages of these fibers to all muscle fiber types differed greatly among fish species, and distributed from 12.9% to 56.53% in a number, and from 2.22% to 53.68% in an area. The relationship between the area and numerical percentages had significantly high positive correlation. Size of the pink muscle fiber was somewhat smaller than that of white muscle fiber.

To clarify the cause of differences in the temporal change of K-value among fish species living in the same habitat water temperature, the influence of the interposition of pink muscle fibers into dorsal ordinary muscle on 5′-inosine monophosphate (5′-IMP) degrading activity was examined. Fourteen fish species from the Sakishima Islands (habitat water temperature 28°C) and from Nagasaki (habitat water temperature 17°C) were used for the sample fishes. Each of 5′-IMP and ρ-nitrophenol phosphate (ρ-NPP) degrading activities showed a peak at near pH 8.0 and near pH 5.0, respectively. These activities were somewhat higher in fish from Nagasaki than in fish from the Sakishima Islands. The interposition percentage of pink muscle fibers into dorsal ordinary muscle correlated significantly (P < 0.05) with the 5′-IMP degrading activity at pH 7.0. Furthermore, the activity at pH 7.0 correlated significantly (P < 0.001) with the increasing rate of K-value at 32°C (ΔK32). These results suggest that the difference in ΔK32 among fish species in the same habitat water temperature might be caused by differences in 5′-IMP degrading activity because of the differences in the interposition rates of pink muscle fibers into dorsal ordinary muscle.

Twenty-seven fish species from the Sakishima Islands and Nagasaki living in water temperatures of 28°C (12 fish species) and 17°C (15 fish species), respectively, were used as sample fishes. Postmortem temporal changes of K-values were measured at 1-h intervals in the dorsal ordinary muscle of each fish, of which the remaining body was then kept in water at a controlled temperature of 32°C. The increasing rate of K-value at 32°C (ΔK32) was calculated from the regression line formed from the relationship between the kept time and the K-value. Muscle fiber types were differentiated by the stability of actomyosin ATPase preincubated in either acid or alkaline conditions. ΔK32 varied widely according to fish species, ranging from 0.98%/h to 14.00%/h. Although the mean value of each body of water was somewhat higher for fishes from Nagasaki at 17°C than in fishes from Sakishima Islands at 28°C, the difference was not significant. The interposition percentage of pink muscle fibers into the dorsal ordinary muscle was also distributed widely, ranging from 0% to 56.53% in number and from 0% to 53.68% in area. A significant correlation was recognized in the relationship between the number or area percentage of pink muscle fibers and deviation percentage of ΔK32 for all fish species sampled; r = 0.411 (P < 0.05) for number percentage and r = 0.518 (P < 0.01) for area percentage. These results suggest that the interposition of pink muscle fibers into the dorsal ordinary muscle might accelerate a temporal change of K-value in fish.

The present study compared and examined the characteristics of actomyosin among white (W), pink (P), and red (R) muscle fiber types in carp (cultured). Both the superprecipitation reaction and the Mg2+-ATPase activity of actomyosin became higher with increased Ca2+ concentration (pCa 7.0–pCa 5.0) and with decreased adenosine triphosphate (ATP) concentration (3.0–0.5 mM) in all three muscle fiber types. A comparison of the three fiber types shows that the superprecipitation reaction of actomysoin was lower in the order of W P > R. A significantly positive correlation between both values was found for each of the three muscle fiber types, but these correlations were clearly different among the three muscle fiber types, and the superprecipitation reaction of actomyosin was lower in the order of W < P < R when Mg2+-ATPase activity was at the same level. In conclusion, the characteristics of actomyosin were remarkably different among white, pink, and red muscle fiber types.