We monitored annual fluctuations of gonadal steroid levels in three sexually mature captive finless porpoises (Neophocaena asiaeorientalis; two males and one female) from two different facilities over 56–91 months. Two animals (one male and one female) were held in an indoor tank with a sunroof (facility A) and the other male was held in an indoor tank without a sunroof (facility B). Water temperatures in both facilities reflected seasonal changes during the study period with a minor difference in the fluctuation pattern. Testosterone levels of the male in facility A were higher from spring to summer every year and exhibited a 12-month cycle. The female showed estrus cycles in 1-month intervals from summer to winter, excluding 2 anestrus years. In contrast, the period of higher testosterone levels of the male in facility B gradually initiated earlier over the years under a constant photoperiod (11.5L:12.5D) and exhibited a 9-month cycle during the first 52 months. After changing the light conditions to a natural photoperiod, its testosterone levels were high from early spring to summer for 3 consecutive years and exhibited a 12-month cycle. Our results showed that under a constant artificial photoperiod, the male in facility B failed to recognize the seasonal changes of a natural external environment, resulting in a 9-month, free-running hormone cycle.

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At Shimonoseki Marine Science Museum, there is no record except for one case as described in detail below of outbreak of Erysipelas infection about 18 years since establishment of our facility in 2001. The case out of 20 individuals of our Cetacean collection (12 Bottlenose Dolphin and 8 Finless Porpoise), Erysipelothrix rhusiopathiae was isolated from one of Finless Porpoise blood sample. The antibody titers against E. rhusiopathiae of Growth Agglutination (GA) of 12 individuals in April 2018 were all less than 16 times. On the other hand, gene fragments specific to E. rhusiopathiae were detected from our frozen foods for marine mammals which was in use as of February 2018. We have been using Neutral PH Electrolyzed Water through storing these food items in refrigerator after thawing, and these results indicate the possibility of suppression for bacterial growth by Neutral PH Electrolyzed Water on E. rhusiopathiae. Keywords: bacterial blood culture, bottlenose dolphin, erysipelas, finless porpoise, food for marine mammal -Jpn J Zoo Wildl Med 24 (4) ：159-162, 2019 ＊ Corresponding author：Hideaki SHINDO