The emergence of multidrug-resistant (MDR) bacterial pathogens poses a major challenge to freshwater aquaculture by compromising fish health, production sustainability and antimicrobial stewardship. This study investigated the phenotypic and molecular characteristics of multidrug-resistant members of the Enterobacter cloacae complex isolated from naturally diseased fish of two cyprinid carps (Labeo rohita and Catla catla) and evaluated the in vitro antibacterial activity of aqueous Curcuma longa extract. Eight naturally diseased fish belonging to two cyprinid carp species were collected from three independent disease outbreaks and subjected to bacteriological examination. Morphological and biochemical analyses, together with 16S rRNA gene sequencing, identified all isolates as members of the E. cloacae complex with 99.86–100% 16S rRNA gene sequence similarity to reference sequences in the NCBI GenBank database. Antimicrobial susceptibility testing against 12 antibiotics demonstrated that all isolates were multidrug resistant, with multiple antibiotic resistance (MAR) indices ranging from 0.25 to 0.33. Universal resistance to tetracycline was observed, whereas all isolates remained susceptible to chloramphenicol, levofloxacin and ofloxacin. PCR analysis detected multiple antimicrobial resistance genes, while phenotypic characterisation revealed isolate-dependent variation in biofilm formation, protease and lipase activities. The aqueous C. longa extract exhibited significant concentration-dependent antibacterial activity, producing inhibition zones of 18.0–20.0 mm at 100 mg mL⁻¹ and minimum inhibitory concentration values of 12.5–25 mg mL⁻¹. These findings identify MDR members of the E. cloacae complex as emerging opportunistic pathogens of two cyprinid carps and highlight the potential of aqueous C. longa extract as a sustainable plant-derived antibacterial agent for freshwater aquaculture.
Post-harvest loss of fish remains a critical challenge affecting food security and economic sustainability in Bangladesh. This study assessed the magnitude and causes of post-harvest loss of hilsa fish across Bangladesh at both the fishers and traders’ levels to estimate physical and market losses and identify the key factors contributing to these losses. A total of 4025 respondents, including 1312 fishers and 2713 traders, were surveyed using structured questionnaires. For data analysis, this research applied the questionnaire loss assessment method (QLAM) and descriptive techniques. Findings showed that the physical and market losses during the capture was 45.06 kg per metric ton (MT), consisting of 1.41 kg physical loss (quantity) and 43.65 kg market loss (economic loss due to reduced selling price). Notably, market loss was higher at the trader level compared with the fisher level. Among all traders’ maximum market loss was found at Bepari level (12.58 kg MT–1), following the retailer level (9.98 kg MT–1) and minimum loss was found at aratder level (2.42 kg MT–1). Quality deterioration and unfavorable market conditions, such as excess supply and reduced demand, were identified as the major contributors to losses. Physical loss mainly resulted from prolonged harvesting time, high temperature, and delayed marketing. The study concluded that post-harvest loss of hilsa was primarily driven by market-related factors rather than physical damage. Improving handling practices, strengthening cold storage facilities, and enhancing market management could reduce these losses and improve economic outcomes.
The present study compared the growth performance, feed utilization, water quality, primary productivity and sediment characteristics of Asian seabass (Lates calcarifer) cultured in an Open-Sea Cage culture system (OSC) and two Integrated Mangrove Aquaculture Systems (MP1 and MP2). Asian seabass were stocked at 10 fish m⁻³ in six HAPAs within each culture system and reared for 60 days. Growth, feed-utilization indices, water-quality parameters, primary productivity and sediment characteristics were monitored throughout the culture period. Body weight increased progressively in all systems, with significantly higher final weight in MP2 (27.01±0.34 g) than in MP1 (25.83±0.30 g) and OSC (23.22±0.11 g). MP2 recorded the highest weight gain, specific growth rate, feed conversion efficiency and protein efficiency ratio, while feed conversion ratio was lowest. Water-quality and productivity characteristics differed significantly among systems and sampling periods, with MP2 showing higher gross and net primary productivity and chlorophyll-a. Sediment characteristics also differed significantly with MP2 recording higher organic carbon, organic matter, total nitrogen and carbon stock. The findings highlight IMAS as a promising production-with-ecological-conservation approach enhancing aquaculture performance while retaining mangrove-based ecosystem functions, thereby supporting environmentally responsible seafood production and progress towards the SDGs.
Chirostoma arge (Jordan and Snyder, 1899) is a fish endemic to the central plateau of Mexico important for fishing in natural reservoirs such as Lake Chapala. Unfortunately, little is known about this species of the Atherinopsidae family, which is listed as Data Deficient by the IUCN Red List. This study’s objective was to determine the sex ratio, the stage of gonadal maturity in each sex, the spawning season and to estimate the relative condition factor, the minimum standard length and the standard length at first maturity. It analyzed a 3195 fish specimens caught by fishers from six landing sites during an annual cycle. The sex ratio was significantly skewed toward males; however, females recorded a higher mean weight and length than males. Spawning in both sexes began in March and lasted until July. The monthly gonadosomatic index values showed significant increases in females and males from January to May. The monthly variation in condition factor showed a significant increase from November to May. The standard length at first maturity or L50 in females (80.4 mm SL) was slightly greater than in males (77.8 mm SL). The mean fecundity was 1778 eggs (±582 SD). A positive correlation was found between fecundity and ovary weight. This study provides biological and fisheries data on the reproductive activity of one of the most abundant species of silverside, C. arge, in Mexico’s largest lake, Lake Chapala.
The present study investigates the seasonal variation in length–weight relationships (LWRs) and condition factors of the brown mussel, Modiolus metcalfei (Hanley, 1843) in the Vellar Estuary of Tamil Nadu, India. Mussels were collected fortnightly during August 2024 – July 2025. The LWRs were analyzed using both non-linear and linear allometry models, and condition status was assessed using Fulton’s condition factor (K) and relative condition factor (Kn). The results revealed a consistent negative allometry growth pattern (b < 3) across all seasons, with b-values ranging from 2.34 (pre-monsoon) to 2.73 (post-monsoon). The coefficient of determination (r2) ranged from 0.8832 to 0.9114, indicating a strong correlation between length and weight. Seasonal variation was also observed in condition factors, with the higher K value was recorded during monsoon and significantly higher Kn was observed during post-monsoon period. These findings suggest that the growth and physiological condition of M. metcalfei are significantly influenced by environmental fluctuations such as salinity, temperature, dissolved oxygen, and food availability. This study provides essential baseline data for understanding the population dynamics and ecological adaptations of M. metcalfei in the Vellar estuarine habitat.
