Spatiotemporal variability in Newfoundland capelin (Mallotus villosus) larval abundance and growth: Implications for recruitment

We examined larval capelin density and growth dynamics in two relatively unstudied northern coastal embayments of Newfoundland (White Bay and Notre Dame Bay), comparing these larval characteristics to those measured in the annually-surveyed Trinity Bay in order to assess the spatiotemporal variability in larval dynamics and its potential implications on subsequent recruitment. We conducted ichthyoplankton surveys in August of 2015 and 2016, assessing larval density and using otolith microstructure analyses to estimate larval age and growth rates. Size of larvae captured over the two years ranged between 4 and 17 mm, corresponding to an estimated age of 1-33 d. Our results indicated substantial spatial and interannual variability in both density and growth. Larval density was similar between bays in 2015 but drastically different in 2016, where the northern bays were characterized by an order of magnitude less larvae than Trinity Bay. Larval growth was significantly higher in the northern bays in 2015, but lower in 2016, relative to Trinity Bay. This spatiotemporal variability in growth, abundance, and survival potential of larval capelin indicates that the proportion of recruits originating from these key spawning areas fluctuates interannually, with potential implications for the assessment and management of the stock.