Paper Reviewed
Sundin, J., Vossen, L.E., Nilsson-Sköld, H. and Jutfelt, F. 2017. No effect of elevated carbon dioxide on reproductive behaviors in the three-spined stickleback. Behavioral Ecology 28: 1482-1491.

According to Sundin et al. (2017), to date there have been "no studies investigating the effects of elevated CO2 on all aspects of the complete breeding cycle of fish." Instead, most ocean acidification experiments focus on only one or two traits, such as reproductive output or success.

In an attempt to remedy this lack of knowledge, the team of four researchers set out to examine the impacts of ocean acidification on the full breeding cycle of pairs of the three-spined stickleback (Gasterosteus aculeatus). This included investigating characteristics of male sexual ornamentation, nest-building behavior, reproductive output and paternal care, comparing observations for fish under either ambient (~400 µatm) or elevated (~1000 µatm) pCO2 conditions.

Results of the experiment revealed that "none of the reproductive variables were affected by the CO2 treatment." More specifically, males subjected to both present and future pCO2 levels (1) "developed normal sexual ornaments," (2) "pursued normal nest building activities," (3, 4) "exhibited similar levels of courtship behaviors and displacement fanning" and (5) "had the same mating probability." Moreover, (6) there was no difference in fanning behavior during the paternal care period and there was (7) "no effect of treatment on the numbers of offspring produced."

In light of the above findings -- or rather the lack of such -- Sundin et al. conclude that "the highly fitness-related functions of reproduction [for G. aculeatus] are robust to elevated CO2, which provides "an optimistic view with regard to fish reproduction [at] future elevated levels of CO2."