Diatom-derived polyunsaturated aldehydes’ effects on the fitness of embryonic and larval surf smelt (Hypomesus pretiosus)

Surf smelt (Hypomesus pretiosus) is a type of forage fish native to the Salish Sea. They are important economically for commercial fishing and ecologically as prey for larger animals and as indicators of ecosystem health. They spawn and develop in shallow coastal environments in close proximity to diatoms, some of which release polyunsaturated aldehydes (PUAs) when broken down. PUAs have previously been shown to negatively affect the development and reproductive success of invertebrates such as copepods, but it is unclear how PUAs affect vertebrate development. The purpose of this study was to test the physiological and morphological effects of increased PUA concentrations on forage fish, specifically surf smelt, in their embryonic and larval stages. To test this, surf smelt were exposed to different concentrations of PUAs in a laboratory experiment. Embryo mortality rates, larval body length, eye size, and otic capsules (sound sensory organs located on the head) were measured. Embryos had increased mortality rates when exposed to high concentrations of PUAs, and larvae had decreased body length and eye size. Other morphological and physiological measurements were taken that produced significant results, but those results are discussed in a separate study. These findings appear to support the hypothesis that increased PUA concentrations decrease embryonic and larval surf smelt fitness. The implications of this study suggest that increased PUA concentrations in the coastal Salish Sea environments could have detrimental effects on forage fish populations.