<div>Background: Macrognathus pancalus or barred spiny eel is a highly valued ornamental and food fish found in the Indian subcontinent. Due to the burgeoning population and their associated impacts, the population of the species is in rapid decline that necessitates time-bound intervention to conserve the species. The current investigation was undertaken to study the gonadosomatic index and gonad histology of Macrognathus pancalus collected from upper Assam, India. 
 
Methods: 500 samples of Macrognathus pancalus were collected from different water bodies such as wetlands, ponds, paddy fields, etc. from upper Assam, India during 2018-2019. Monthly samplings were carried out to evaluate the gonadosomatic index. The gonads were dissected out, measured and subsequently preserved for histological studies. Histological sections of preserved samples were prepared by employing accepted methodologies. The sections were then photographed using Leica DM 750 and gonadal staging was ascertained.&nbsp; 
 
Result: Gonadosomatic index studies revealed that it peaked in August in both males (3.45&plusmn;0.18) and females (8.85&plusmn;0.35), thereby indicating its spawning season. Minimum GSI values were observed during January in males (0.39&plusmn;0.04) and in December in females (1.04&plusmn;0.15) indicating the culmination of the breeding period and the advent of the preparatory phase. Macroscopic and microscopic examination unearthed five different phases of gonadal maturation. Gonadal staging through microscopic and macroscopic technique showed synchronicity with GSI values.&nbsp;</div>

<div>Investigations on Gonadosomatic Index and Gonad Histology of Barred Spiny eel Macrognathus pancalus Hamilton, 1822 from Upper Assam, India</div>

Background: The objective of the study was to examine the growth and development of M. pancalus larvae in captive conditions, including pigmentation patterns, yolk and oil globule utilization, growth rates and metamorphosis, as well as to identify suitable live food for larviculture. 
 
Methods: The larvae, produced through induced breeding, were kept unfed until the yolk-sac absorption and then fed with freshwater rotifer, mixed zooplankton and Tubifex worms at different stages of development. The larvae were reared in indoor glass tanks and outdoor reinforced plastic tanks to document their morphological and chronological development. 
 
Result: The findings showed that the larvae exhibited typical characteristics of eel. Notably, dentition was observed before yolk resorption, indicating the highly predatory nature of the larvae. The bands of melanophores, which were prominent at the beginning, disappeared between 5-7 days post-hatch. Additionally, the study identified distinct features of spiny eels, such as a trunk-like rostral projection at 14 days post-hatch and erectile dorsal spines at 21 days post-hatch. The growth pattern, morphological changes and adaptation to benthic burrowing habits indicated that the larvae metamorphosed into the fry stage between 28-45 days post-hatch. These results provide valuable insights into the ontogenetic development and rearing of M. pancalus and can be used to support future aquaculture and conservation programs.

Investigations on Gonadosomatic Index and Gonad Histology of Barred Spiny eel Macrognathus pancalus Hamilton, 1822 from Upper Assam, India

Ontogeny and Growth of Early Life Stages of Barred Spiny Eel Macrognathus pancalus (Hamilton, 1822)