Minnows may be more reproductively resilient to climatic variability than anticipated: Synthesis from a reproductive vulnerability assessment of Gangetic pool barbs (Puntius sophore)

摘要

Information on various aspects of reproductive traits of female pool barbs from various stretches of Ganga River basin, India was generated in relation to climatic variability. The presumptions surrounding - minnows being the first and easily hit by climatic variability, was validated. GAM models revealed low threshold rainfall requirement (> 50 mm) within a wide temperature range (20-30 degrees C) necessary for attainment of breeding GSI (> 10.5 units). Pre-spawning fitness (K-spawn50) and size at 50% maturity (L-M(50)) benchmarked through Kaplan-Meier survival estimates were in the range 1.61-1.67 units (Fulton condition factor) and 8.6-9.0 cm respectively. Mapping of climate preferendum through LOESS smoothing hinted both low-mild rainfall (50-150 mm) and high rainfall conditions (400-700 mm) conducive for attaining pre-spawning fitness while no dependence on temperature was observed. First maturity of females was encountered at 4.7 cm within the size range 4.4-12.6 cm. The present study hinted a probable reduction (1.4-1.8 cm) in size at maturity of female pool barbs. We observed pool barbs can breed within a wide thermal regime following slightest of rainfall events. Collating this with the present rates of climatic variability, we infer negligible threat of changing climate on reproduction of Puntius sophore in near future - contrary to the existing presumptions. Owing to the easiness in attainment of pre-spawning fitness under an apparently flexible climate preferendum, 'skipped spawning' decisions while facing climatic variability also seem minimum. The recorded breeding thresholds may serve as future references while assessing climate driven changes on reproduction and evolutionary adaptations in Gangetic minnows.