Effects of Prolonged Fasting and Refeeding on Metabolic, Physiological, Tissue, and Growth Performance Adjustments in Colossoma macropomum

Given recent declines in North Pacific humpback whale (Megaptera novaeangliae) reproductive output and calf survival, there is additional urgency to better understand how mother–calf pairs allocate energy resources across their migratory cycle. Here, unoccupied aerial system (UAS; or drone) photogrammetry was used to quantify the body size and condition (BC) of humpback whales on their Hawaiʻi (HI) breeding and Southeast Alaska (SEAK) feeding grounds. Between 2018 and 2022, we collected 2410 measurements of 1659 individuals. Rates of change in body volume (BV) and length (BL) were quantified using 803 repeat measurements of 275 individuals. On average, HI mothers lost 0.106 m3 or 96.84 kg day−1 while fasting, equivalent to 2641 MJ day−1 or 830 kg of krill and 424 kg of Pacific herring daily. HI calf BV and BL increased by 0.035 m3 and 2.6 cm day−1, respectively. In SEAK, maternal BV increased by 0.015 m3 or 14.54 kg day−1 (367 MJ day−1), while calf BV and BL increased by 0.039 m3 and 0.93 cm day−1, respectively. Maternal investment in calf growth correlated with both female BL and BC, with larger females producing larger, faster‐growing calves. Finally, using 330 measurements from 156 females, we quantified differences in BC increase over four feeding seasons. Lactating females exhibited an average BC increase of 6.10%, half that of unclassified females (13.51%) and six times lower than pregnant females (37%). These findings represent novel insights into the life history of humpback whales across their migratory cycle, providing key baseline data for bioenergetic models elucidating the effects of anthropogenic disturbance and rapidly changing ocean ecosystems. imageKey points On average, Hawaiʻi (HI) mothers lost 0.106 m3 or 96.84 kg day−1, equivalent to 2641 MJ day−1. Over a 60 day period, this corresponded to an estimated mean energetic cost of 158 GJ, or ≈50 tons of krill or ≈25 tons of Pacific herring, surpassing the total energetic cost of gestation estimated for humpback whales of similar length. In Southeast Alaska (SEAK), maternal body volume (BV) increased by just 0.015 m3 or 14.54 kg day−1 (367 MJ day−1). Further, SEAK lactating females showed the slowest rates of growth in body width and condition over a 150 day period compared to non‐lactating females. Maternal investment in calf growth correlated with both maternal length and body condition, with larger females producing larger, faster‐growing calves. In HI, however, the ratio between maternal BV lost and calf BV gained (conversion efficiency) was relatively low compared to other mammals.

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Use of the essential oil of Thymus vulgaris (thyme) and its nanoemulsion as an anesthetic during the cultivation of tambaqui (Colossoma macropomum): Anesthesia induction and recovery curve, physiology, performance and feed consumption

Boaventura,

Oliveira,

Santos

et al. 2024

Preprint

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The thymol chemotype of the essential oil of Thymus vulgaris (EOTV-T) and its nanoemulsion (NEOTV-T) were investigated as anesthetics in the management of Colossoma macropomum. The stability of nanoemulsions was analyzed by zeta potential and dynamic light scattering for an interval of 37 days prior to carrying out two anesthesia experiments. The first experiment determined anesthesia induction and recovery intervals for juveniles anesthetized with different concentrations of EOTV-T and NEOTV-T. Based on the obtained induction and recovery curve, the second experiment adopted concentrations of 75 mg/L of EOTV-T and 50 mg/L of NEOTV-T for use during biometric management every 10 days for 60 days of cultivation of juvenile C. macropomum. The results showed that NEOTV-T had an average diameter of less than 100 nm for up to 22 days and was more effective at inducing anesthesia than EOTV-T. The continuous use of anesthetics during biometrics did not affect juvenile performance in terms of growth, feed consumption and survival. Furthermore, no significant differences were observed in hematological and biochemical parameters between juveniles of the control treatment and those subjected to biometric management using 75 mg/L of EOTV-T and 50 mg/L of NEOTV-T. It can be concluded that the essential oil of T. vulgaris and its nanoemulsion can be used to facilitate the management of juvenile C. macropomum without compromising their performance or well-being. More studies need to be carried out to improve the stability of nanoemulsions of the essential oil of T. vulgaris and to evaluate their effects on acute stress.

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Effects of Prolonged Fasting and Refeeding on Metabolic, Physiological, Tissue, and Growth Performance Adjustments in Colossoma macropomum

Cited by 3 publications

References 51 publications

Use of the essential oil of Thymus vulgaris (thyme) and its nanoemulsion as an anesthetic during the cultivation of tambaqui (Colossoma macropomum): anesthesia induction and recovery curve, physiology, performance, and feed consumption

Use of the essential oil of Thymus vulgaris (thyme) and its nanoemulsion as an anesthetic during the cultivation of tambaqui (Colossoma macropomum): anesthesia induction and recovery curve, physiology, performance, and feed consumption

Maternal investment, body condition and calf growth in humpback whales

Use of the essential oil of Thymus vulgaris (thyme) and its nanoemulsion as an anesthetic during the cultivation of tambaqui (Colossoma macropomum): Anesthesia induction and recovery curve, physiology, performance and feed consumption

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