Suspended sediment transport generated by non-hydrostatic hydrodynamics in Northern Waters of Aceh, Indonesia.

Suspended Sediment transport in the Northern Waters of Aceh is investigated in the domains between 5.4° - 5.65° N Latitude and 95.15° - 95.45° E. Therefore, this study aims to calculate the suspended sediment transport using a non-hydrostatic hydrodynamic model with an output distribution of total suspended sediment concentration. The model was run using tidal components of M2, S2, K1, O1, N2, K2, P1, Q1 and the wind every 6 h in February and August 2019 representing the North East and South West monsoons, as well as sea temperature and salinity data. The results of the model correlated with the Tide Model Driver data obtained, and the simulation results indicated the current in February 2019 is different than in August. The numerical simulation results show that the distribution of suspended sediments in Northern Waters of Aceh is driven by currents. Furthermore, the hydrodynamics and the designed model showed that the distribution value of the surface total suspended sediment concentration was lower in August than in February 2019. The verification results of the surface total suspended sediment concentration between the model and the Visible Infrared Imaging Radiometer Suite showed a good match. These results can facilitate the analysis of limited observation and remote sensing data.

Lernaea cyprinacea Linnaeus, 1758 (Copepoda: Lernaeidae) infection on Betta rubra Perugia, 1893 (Anabantiformes: Osphronemidae) from Aceh Province, Indonesia.

Betta rubra is an ornamental freshwater fish endemic to northern Sumatra, Indonesia. The B. rubra population has decreased in recent decades, and is classified as an endangered species in the IUCN Red List. This study aims to report for the first time infection by L. cyprinacea in B. rubra harvested from the Aceh Besar region of Indonesia. The fish samples were obtained from the Cot Bira tributaries, Aceh Besar District, Indonesia from January to December 2020. The results showed that the parasite infected 6 out of 499 samples in August and September, with a prevalence and intensity rate of 1% and 2 parasites/fish, respectively. The eyes and pectoral fins were the common infection sites. Despite B. rubra is not an optimal host (small size) for the parasite, this parasite might serve as additional threatening factors for the endangered B. rubra fish population.

Lernaea cyprinacea Linnaeus, 1758 (Copepoda: Lernaeidae) infection on Betta rubra Perugia, 1893 (Anabantiformes: Osphronemidae) from Aceh Province, Indonesia / Infecção por Lernaea cyprinacea Linnaeus, 1758 (Copepoda: Lernaeidae) em Betta rubra Perugia, 1893 (Anabantiformes: Osphronemidae) provenientes da província de Aceh, Indonésia

Abstract Betta rubra is an ornamental freshwater fish endemic to northern Sumatra, Indonesia. The B. rubra population has decreased in recent decades, and is classified as an endangered species in the IUCN Red List. This study aims to report for the first time infection by L. cyprinacea in B. rubra harvested from the Aceh Besar region of Indonesia. The fish samples were obtained from the Cot Bira tributaries, Aceh Besar District, Indonesia from January to December 2020. The results showed that the parasite infected 6 out of 499 samples in August and September, with a prevalence and intensity rate of 1% and 2 parasites/fish, respectively. The eyes and pectoral fins were the common infection sites. Despite B. rubra is not an optimal host (small size) for the parasite, this parasite might serve as additional threatening factors for the endangered B. rubra fish population.

Resumo Betta rubra é um peixe de água doce ornamental endemico da região norte Sumatra, Indonesia. A população de Betta rubra diminuiu ao longo dos anos, sendo classificada como espécie em extinção na Lista Vermelha da IUCN. Este estudo tem como objetivo relatar pela primeira vez infecção por L. cyprinacea em B. rubra coletados na região de Aceh Besar na Indonésia. As amostras de peixes foram obtidas nos afluentes Cot Bira, distrito de Aceh Besar, Indonésia de janeiro a dezembro de 2020. Os resultados mostraram que o parasito infectou 6 das 499 amostras em agosto e setembro, com uma prevalência e taxa de intensidade de 1% e 2 parasitas/peixes, respectivamente. Os olhos e as nadadeiras peitorais foram os sítios de infecção mais comuns. Apesar de B. rubra não ser um hospedeiro ideal (pequeno tamanho) para o parasita, este parasita pode servir como fator de ameaça adicional para a população de peixes B. rubra, ameaçada de extinção.

Numerical study of tides in the Malacca Strait with a 3-D model.

Malacca Strait (MS) has an important role and potential for many countries. It is a major transportation route for oil and commodities across continents. In addition, various activities such as shipping, fishing, aquaculture, oil drilling, and energy are also carried out in MS. Tides strongly affect the MS environment so that it becomes a major parameter in MS management. This paper is the first study, which presents MS tidal hydrodynamics based on a baroclinic and nonhydrostatic approach. Tidal hydrodynamics in MS and the surrounding waters were assessed using tidal forces, temperature, salinity, and density. This study analyzes the amplitude, phase, current ellipses, and semi-major axis of the tides. These variables are obtained from the simulation results of the three-dimensional numerical models of M2 tides and combined tides (M2, S2, N2, K1, and O1) with nonhydrostatic models. Then the results obtained are verified by observation data. Amplitude and phase of the tidal wave in MS originate from two directions, namely the northern part of MS (Andaman Sea) and the South China Sea (SCS). Tides from the north of MS propagate into the MS, while tides from the SCS travel to Singapore Waters (SW) and the south of MS. This causes a complex residual flow in SW and shoaling in the middle of MS. Shoaling in the middle of MS is characterized by a large amplitude and semi-major, as in B. Siapiapi. The results of this analysis show that tidal waves are dominated by semidiurnal types rather than diurnal types. The M2 current ellipse has dominantly anticlockwise rotation along the west of the MS, while along the east of MS, it has generally a clockwise rotation.

Length-weight relationships and condition factors of mullets Liza macrolepis and Moolgarda engeli (Pisces: Mugilidae) harvested from Lambada Lhok waters in Aceh Besar, Indonesia.

Background: The mullets fish Liza macrolepis and Moolgarda engeli are predominant in the Lambada Lhok waters in Aceh province. At present, no scientific report on this species in Aceh waters is available. Therefore, the objective of the present study is to examine the growth pattern and condition factor of the species of mullets L. macrolepis and M. engeli harvested from the aforementioned coastal waters. Methods: The sampling was done in three locations in the Lambada Lhok waters from July to November 2018. The fish were captured using gillnets from 6:00 AM to 3:00 PM four times a month for five months.  A total of 242 L. macrolepis and 109 M. engeli were used for the analysis. The growth pattern was analyzed using linear allometric model; then, two condition factors, Fulton's and relative weight, were calculated. Results: The study revealed a b value of 2.49 for the male L. macrolepis and 1.81 for the female. The b value was 3.22 for the male M. engeli and 3.41 for the female. The b value of the fish was higher during the dry season. The Fulton's condition factor of the male L. macrolepis was 1.19, and that of the female was 1.19. The relative condition factor of this species was 100.11 and 100.01 for males and females, respectively. The Fulton condition factor of male M. engeli was 1.05 and that of the female was 1.06. The relative weight condition factors were 101.08 and 100.61 for the male and female, respectively.   Conclusions: The growth pattern of  M. engeli tends to be isometric, whereas that of  L. macrolepis has a negative allometric growth pattern. The condition factors indicate that the Lambada Lhok waters are still in good condition and support the growth of the mullets, but  M. engeli is more adaptable than  L. macrolepis.

The dynamics of surface wave propagation based on the Benjamin Bona Mahony equation.

Modulation instability is one of the consequences of the water medium's inclination. It causes surface water waves to run into phenomena of splitting and merging in their propagation. An increase in wave amplitude follows this phenomenon, which can encourage the appearance of extreme waves. It is known that the Benjamin Bona Mahony (BBM) wave has modulation instability in its propagation, with the envelope evolving by the equation Nonlinear Schrodinger (NLS) equation dynamic. One of the NLS equation solution is known as Soliton on Finite Background (SFB). SFB is a continuation of the Benjamin-Feir nonlinear terms. Here, the probe of the BBM wave dynamics is conducted by transforming the complex amplitudes form of SFB variable into the polar form of displaced phase-amplitude. It was done to observe changes in the amplitude of the wave in a complex plane with phases that depend only on position. The description of the dynamics of the SFB can be illustrated through Argand diagrams. It was found that the modulation frequency affects the SFB phase: the smaller the modulation frequency, the higher the phase angle. Also, it is found that the phenomenon of SFB phase singularity occurs in extreme waves for certain frequency modulation intervals.