MEPS 516:153-161 (2014)  -  DOI: https://doi.org/10.3354/meps11003

ABSTRACT: Abundance, size and developmental stage data for furcilia and juvenile euphausiids together with data on the timing and prevalence of attached spermatophores on adult females are used to infer times of spawning by 4 euphausiid species in Frederick Sound and lower Stephens Passage, Southeast Alaska. Results from net tows conducted between late May and September 2008 and a single, opportunistic dip-net sample on 21 April indicate that Thysanoessa raschii and T. longipes spawned in association with the spring phytoplankton bloom in April and continued spawning until June, with juveniles first appearing in mid- to late June. Presence of female T. spinifera carrying spermatophores in mid-April indicates that T. spinifera spawns in association with the spring bloom as well; however, absence of larval T. spinifera suggest that spawning in the inshore waters is comparatively rare. In contrast, observations of female Euphausia pacifica carrying spermatophores from late May to August and the first appearance of early furcilia in August indicate that spawning occurs, at least to some extent, after the primary bloom. However, the appearance of juvenile E. pacifica in late June suggests that spawning occurred earlier as well and in discrete bouts. We argue that the absence of E. pacifica furcilia that were likely to have originated from an early spawning event may indicate that E. pacifica juveniles observed in late June were advected into the study region from the Gulf of Alaska. Overall, phenology of seasonal reproduction in this Alaskan fjord is similar to that observed in coastal waters in arctic and temperate ecosystems.

KEY WORDS: Euphausiids · Southeast Alaska · Spawning timing · Juvenile · Larva · Fjord