International Journal of Aquatic Biology

Indigenous techno-vention to promote periphyton-based aquaculture

Sandipan Gupta — 2024-06-25

Considering the increasing demand for aquaculture production, semi-intensive and intensive cultures have already been established, but with enhanced cost of supplementary and complete feed and associated incidence of water quality deterioration due to accumulated nutrient loss, an alternative approach of periphyton-based aquaculture has been initiated. Periphyton-based aquaculture is a low-cost culture technique with less feed input and has been reported to support the high production of most cultured fish species. Apart from this, an improved level of water quality in periphyton-based aquaculture has also been reported. Even considering these advantages, periphyton-based aquaculture has not been implemented on a huge scale due to one major disadvantage: the stationary nature of the substrate on which the biofilm grows. For this reason, partial harvesting of the stock or regular management practices of the cultured pond is impossible as these require complete removal of the substrates. To solve this problem, a model with indigenous technical intervention has been proposed where any substrate, bio-degradable or non-biodegradable so far, used for periphyton-based aquaculture can be used. Though this model is handy using bamboo poles and split bamboos; other components like crushed sugarcane bagasse, paddy straw, and PVC pipes can also be incorporated into it.

Demographics of threatened Malabar mahseer, Tor malabaricus in a small-scale fisheries of Western Ghats hot spot in India

Chelapurath Radhakrishnan Renjithkumar — 2024-06-25

The Western Ghats region of India, a segment of the Western Ghats-Sril Lanka biodiversity hotspot, is renowned for its abundant fish diversity and endemism. Tor malabaricus, commonly known as Malabar mahseer, is a large growing, threatened cyprinid having restricted distribution in fast-flowing streams of the southern region of the Western Ghats. The absence of demographic and exploitation data regarding threatened freshwater fish in this region is a barrier to sustainably managing and conserving the species. This study focused on assessing the growth patterns, mortality rates, and the extent of exploitation faced by the Malabar mahseer from a small-scale fishery in Chalakudy River, WG, India, with the help of tribal fishers. The growth parameters for T. malabaricus were estimated as asymptotic length (L?) = 657.3 mm and growth rate (K) = 0.19 year^-1. The study revealed a potential longevity (t_max) of 15.78 years and a length at first capture (L_c) of 201.54 mm. The fishing mortality (F= 0.26 year^-1) of T. malabaricus was observed to exceed the natural mortality (M = 0.23 year^-1), indicating an unsustainable level of exploitation for the species within the study area. The current exploitation rate (E = 0.53) exceeding the E₅₀ threshold indicates a potentially uncertain future for the stock under the current level of exploitation. Employing an integrative conservation approach such as fishing closures during spawning seasons, mesh size regulations, and establishing quota systems for local tribes and fishermen for fishing can effectively promote sustainable harvesting practices for the species within the Western Ghats hotspot.

The effects of Excoecaria agallocha extract on growth, innate immune responses, and resistance to Vibrio parahaemolyticus in white shrimp, Litopenaeus vannamei

Thi Tuyet Minh Vo — 2024-06-25

The purpose of this study is to determine the effects of supplementary Excoecaria agallocha extract (EAE) on growth performance, innate immune responses, and resistance to Vibrio parahaemolyticus in white shrimp, Litopenaeus vannamei. Shrimp were separated into four groups, with each group fed diets containing different concentrations of 0 (control), 20 (EAE20), 30 (EAE30), and 40 (EAE40) g kg^-1. The results indicated that shrimp fed diet containing different concentrations of EAE did not affect growth performance and survival rate for a 56-day feeding trial. However, shrimp fed a diet containing EAE20 showed increased HC, GC, THC, PO activity, and Phagocytic rate on days 1, 3, 7, 14, and 28. Moreover, supplemented different concentrations of EAE in the diets showed increased resistance to V. parahaemolyticus infection of white shrimp after 56 days of feeding. The results indicate that EAE could be applied to shrimp feed to enhance immune response and resistance to bacterial disease.

Distributional range extension of Hypostomus nigropunctatus Garavello, Britski & Zawadzki, 2012 (Siluriformes: Loricariidae): New record for Argentina

Pablo Agustin Burchardt — 2024-06-25

Hypostomus nigropunctatus is a loricarid species distributed in the Río Iguazú basin in Brazil. We revised some specimens from the Arroyo Urugua-í basin, Misiones, Argentina, which, based on a morphological comparison, are corroborated to be H. nigropunctatus. These specimens expand the species' known distribution from the Iguazú basin to the Urugua-í basin. Furthermore, this finding is the first record of this species in Argentina.

The histology and surface morphology of the olfactory organ in Silond catfish, Silonia silondia (Hamilton, 1822)

Saroj Kumar Ghosh — 2024-06-25

Histological and scanning electron microscopy techniques were employed to study the olfactory organ of Silonia silondia (Siluriformes: Schilbeidae). The thorough examination revealed a well-developed olfactory organ characterized by a series of intricately arranged lamellae that were elegantly inserted into a narrow midline raphe, forming an elongated rosette structure. It comprised the olfactory lamellae, adorned with olfactory epithelium and a distinct median raphe. On each lamella, sensory and nonsensory epithelium were distinctly segregated. The dorsal lamellar processes housed the sensory area, while the nonsensory area enveloped the remainder of the olfactory lamellae. Histologically, each lamella exhibited a central lamellar space, enveloped on either side by olfactory epithelium characterized by receptor cells, supporting cells, lymphatic cells, mast cells, mucous cells, and basal cells. The sensory epithelium contained three morphologically distinct receptor cells: ciliated, microvillous, and rod types. The cellular organization of the olfactory lining was explored in conjunction with the chemosensory system of the fish under investigation.

Novel isolation of Enterococcus spp. from common carp, Cyprinus carpio in Iraq: Antibiotic resistance and susceptibility to Syzygium aromaticum

Sadeq M. Al-Haider — 2024-06-25

The aquaculture industry, particularly in high-density and intensive settings, has suffered significant economic setbacks due to various bacterial diseases. Consequently, it is imperative to investigate the presence of pathogenic species, accurately identify them, and evaluate their resistance to antibiotics or natural extracts to safeguard fish populations. This study aimed to examine 120 specimens of common carp, Cyprinus carpio, collected from two cage farms along the Al Hillah River in Babil Governorate, Iraq, during August, September, and October 2023. Swabs were collected from the skin, gills, and intestines for bacterial culture, followed by isolation and identification using the VITEK 2 system. Sensitivity testing was conducted on the isolated bacteria, and the susceptibility of plant cloves, Syzygium aromaticum, was assessed as a natural extract. The findings indicated the isolation of two Enterococcus species, namely E. gallinarum and E. casseliflavus, from the fish's gills, intestines, fins, and skin. Antibiotic susceptibility testing revealed that the bacteria were sensitive to the minimum inhibitory concentrations (MIC) of imipenem, ciprofloxacin, levofloxacin, and trimethoprim/sulfamethoxazole, while exhibiting resistance to cefoxitin and cefazolin. The susceptibility of the plant clove was evaluated using the disc diffusion method on blood agar, measuring the diameter of the inhibition zone to assess the effectiveness of alcohol-extracted clove at four concentrations: 10%, 15%, 20%, and 25%. The results showed that S. aromaticum extract effectively inhibited infections caused by E. gallinarum and E. casseliflavus, particularly at the highest concentration of 25%. The findings of this study provide compelling evidence for the existence of E. gallinarum and E. casseliflavus in common carp farming in the Hilla River, marking their first isolation in Iraq. Furthermore, the research assessed the susceptibility and resistance of these bacterial strains to various commonly used antibiotics. Additionally, the investigation included an evaluation of clove extract as a botanical agent, which demonstrated antimicrobial activity against intestinal bacteria across a range of concentrations.