Impacts of Sea Temperature Rise on Rastrelliger kanagurta Potential Fishing Grounds in the Exclusive Economic Zone (EEZ) Off South China Sea

The Indian mackerel (Rastrelliger kanagurta) is one of the most commercially crucial epipelagic scombrid where it is caught in the Exclusive Economic Zone (EEZ) off the South China Sea (SCS). High demand for fisheries resources is a challenge for fishers to achieve optimal fish landing targets. By using R. kanagurta catch data, and high resolution satellite data of chl-a and SST (MODIS-Aqua) and SSH (AVISO) from 2018 together with boosted regression tree (BRT) model, this study aims to determine the impact of sea surface temperature (SST) increase on the potential catch of R. kanagurta based on temperature projection of IPCC-AR5-RCPs scenarios. BRT modelling result indicated that during the northeast monsoon (NEM), at elevated temperature of 1.80 and 2.60 ℃ showed that the potential fishing grounds of R. kanagurta increase in the area especially in the northern part of the EEZ. However, at elevated temperature of 3.30 ℃, the potential fishing areas was found to decrease along the coast of Peninsular Malaysia. Meanwhile, during southwest monsoon (SWM) and inter-monsoon transition, at temperature rise of 1.80, 2.60 and 3.30 °C showed a significant reduction in the potential fishing area of the R. kanagurta potential fishing grounds especially along the coast of the EEZ off SCS. Results indicated that changes in SST influenced suitability of habitat which affected the distribution of R. kanagurta. Understanding the impacts of temperature increase would contribute towards future sustainable fisheries resource management strategies.

Analisis timbal, kadmium dan formaldehid pada ikan asin petek (leiognathus equulus) dan ikan asin kembung (rastrelliger kanagurta) di Pulau Cangkir Kronjo

Ikan asin merupakan produk hasil perikanan dengan bahan baku ikan segar yang mengalami pengawetan dan menjadi salah satu sumber protein hewani yang banyak dikonsumsi masyarakat seperti ikan asin Petek dan ikan asin Kembung. Mutu dari ikan asin dapat ditentukan dari cara penjual mengolahnya serta kondisi lingkungan. Penelitian ini bertujuan untuk mengetahui kadar timbal, kadmium dan formaldehid pada ikan asin petek dan kembung di daerah Pulau Cangkir Kronjo, Banten, Indonesia. Analisis timbal dan kadmium dilakukan dengan metode spektrofotometri serapan atom sedangkan analisis formaldehid dilakukan dengan metode spektrofotometri UV-Vis. Hasil penelitian menunjukan ikan asin petek dan kembung tidak mengandung logam timbal dan kadmium akan tetapi mengandung formaldehid, pada ikan asin petek 2.843,24 ± 71,9510 mg/Kg dan ikan kembung 865,96 ± 4,4479 mg/Kg. Dari pengujian tersebut baik pada ikan asin petek dan kembung tidak ada cemaran timbal dan cadmium karena dibawah nilai ambang batas maksimum sedangkan kandungan formaldehidnya cukup tinggi dan berbahaya bagi kesehatan.

Reduced Washing Cycle for Sustainable Mackerel (Rastrelliger kanagurta) Surimi Production: Evaluation of Bio-Physico-Chemical, Rheological, and Gel-Forming Properties

Although dark muscle is currently the most important obstacle in marketing high-quality Indian mackerel (Rastrelliger kanagurta) surimi, reducing washing remains a challenge for long-term surimi production from this species. Herein, the impact of washing cycles (one (W1), two (W2), and three (W3) cycles) with a 1:3 mince to water ratio on the bio-physico-chemical properties, rheology, and gelling ability of mackerel surimi was evaluated. The yield, Ca2+-ATPase activity, TCA-soluble peptide, and myoglobin contents of surimi decreased as the number of washing cycles increased, while lipid removal, reactive SH content, and surface hydrophobicity of surimi increased. Surimi generated by W2 and W3 provided the same rheological patterns and Fourier-transform infrared spectroscopy (FTIR) spectra as unwashed mince, with the highest gel strength and whiteness, as well as the lowest expressible drip, thiobarbituric acid reactive substances (TBARS), and fishy odor. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) demonstrated the presence of polymerized proteins stabilized by disulfide and other interactions. Using a scanning electron microscope, several concentrated dense areas and distributed pores generated by myofibrillar proteins gel networks were found. Surimi from W2 and W3 appeared to be of similar overall quality, however W2 had a larger yield. As a result of the evaluation of bio-physico-chemical, rheological, and gel-forming capabilities, as well as product yield, W2 may be the best option for producing high-quality surimi from Indian mackerel in a sustainable manner.

Biomedical applications of fish gut associated Streptomyces maritimus IM20 isolated from Rastrelliger kanagurta (Indian mackerel)

The biomedical potential of fish gut-associated actinobacteria isolated from the marine fish Rastrelliger kanagurta (Indian mackerel) was investigated. The actinobacterial strain IM20 was isolated from the fish gut by using Kusters agar medium prepared with 50% sea water. Based on their phenotypic and molecular characteristics, strain IM20 was identified as Streptomyces maritimus. The bioactive metabolites produced from the strain IM20 by agar surface fermentation and ethyl acetate extraction were tested for in vitro antimicrobial, antiquorum sensing , anti-biofilm, anti TB, anti-oxidant and anti-cancer activity. The MIC value of ethyl acetate extract (EAE) of IM20 was found to be 16 μg ml−1 against S. aureus and E. coli. In quorum sensing inhibition assay, the extract showed violacein inhibition upto 87% at 512 μg ml−1 concentration when tested by pigment inhibition assay using C. violaceum MTCC 2656. The results of in vitro assays revealed that the ethyl acetate extract of IM-20 (EAE-IM20) showed 75%, 83% and 72% inhibition against Mycobacterium tuberculosis H37Rv, M. tuberculosis (SHRE sensitive) and multi drug resistant (MDR) M tuberculosis respectively at 500 μg ml−1 concentration. In DPPH assay, 71% radical scavenging activity was exhibited by the EAE-IM20 at 250 μg ml−1. In MTT assay, EAEIM20 exhibited 74.29±2.01% inhibition on breast cancer cell line MCF7 (250 μg ml−1). This study broadly determines that the fish associated actinobacteria is a prolific place for diverse multifunctional bioactive compounds for the development of medically important unique drugs.

A study on ectoparasites in Indian Mackerel, Rastrelliger kanagurta (Cuvier, 1817) of Thiruvananthapuram coast, South India

Parasitic infestation in marine fish requires urgent attention, especially those that infect economically important fishes, which affect their aesthetic quality and palatability. Ectoparasites in Indian Mackerel, Rastrelliger kanagurta (Cuvier, 1817), have not been studied well. Morphological and seasonal study of ectoparasites in R. kanagurta from the Thiruvananthapuram coast was conducted during March-August 2018. The study investigated three parasitic groups: Trichodinids, Digenean cysts (Centrocestus Looss, 1899), and Cymothoids (Norileca indica Milne Edwards, 1840 and Nerocila phaiopleura Bleeker, 1857) from R. kanagurta during the present study. Of the 240 fishes examined, the Trichodinids and digeneans showed 100% prevalence on the gill samples. Seasons had no significant effect on trichodinids and digeneans prevalence. However, parasitic Cmothoids fluctuated significantly according to the season. They showed greater prevalence during the pre-monsoon (45%) and least in monsoon (25%) due to environmental parameters like rainfall, salinity, and temperature. Trichodinids parasitized gills of R. kanagurta showed increased mucus production, paleness in the gills, and multifocal whitish areas. The Cymothoid infested fish showed lesions with the erosion of the epidermis and underlying dermis at the site of attachment. The noticeable changes were observed in the gill epithelium due to the encystment of digeneans. The Trichodinid ciliates and Heterophyid digenean cysts (Centrocestus Looss, 1899) are reported for the first time in R. kanagurta.

Pemetaan Zona Daerah Penangkapan Ikan Dengan Bagan Perahu Cungkil Berdasarkan Time Series Pada Perairan Teluk Bone

Penelitian ini bertujuan untuk mengidentifikasi aspek teknik bagan perahu cungkil, pemetaan zona daerah penangkapan ikan berdasarkan time series bulanan, komposisi hasil tangkapan target spesies berdasarkan time series bulanan dan komposisi hasil tangkapan target spesies berdasarkan jarak dan kedalaman perairan. Penelitian dilaksanakan Maret 2020 - Februari 2021, lokasi penelitian di Teluk Bone. Data dipetakan menggunakan rekaman posisi pada GPS yang kemudian di overlay kedalam tampilan aplikasi Novianic Asia Afrika. Penelitian bertujuan untuk mengidentifikasi aspek teknis bagan perahu cungkil, pemetaan zona daerah penangkapan ikan berdasarkan time series bulanan, komposisi hasil tangkapan berdasarkan musim jarak dan kedalaman perairan. Hasil analisis menemukan bahwa alat tangkap bagan cungkil termasuk kedalam klasifikasi bagan perahu sama seperti bouke ami dengan metode pengoperasiannya menggunakan lampu (light fishing) sebagai daya tarik mengumpulkan ikan yang bersifat (phototaxis), zona Daerah Penangkapan Ikan (DPI) berdasarkan time series bulanan memperlihatkan kosentrasi penangkapan berada pada perairan pesisir timur Teluk Bone, Proporsi ikan banyak tertangkap didominasi Ikan Teri (Steleporus devisi), Cumi-cumi (Loligo sp), Tembang (Sardinella fimbriata) dan kosentrasi tertangkap pada jarak 0,4 – 2,4 mill dengan kedalaman 15 – 50 meter dan Tongkol lisong (Auxis rochei), Layang (decapterus ruselli) dan Kembung (Rastrelliger kanagurta) dengan jarak 12 - 24 mil dari pantai pada kedalaman ≥ 200 meter.