Abstract
Larval drift is a key process for successful fish recruitment. We used Norwegian spring-spawning herring (Clupea harengus) as model species to investigate the relationship between larval drift and recruitment. Larval drift indices were derived from simulations based on survey observations between 1993 and 2016. We show that forward simulated larval drift indices have an important positive relation to recruitment success. The relationship demonstrates elevated recruitment when larvae relocate rapidly northwards toward the Barents Sea. Negative or low larval drift indices coincide with only weak recruitment emphasizing limited survival in years with enhanced larval retention. Hence, with this work we combine drift model outcomes refined with survey data indicating that more extensive larval drift is an important component in population dynamics for high-latitude small pelagic fishes. However, larval displacement alone represents only one among many controlling factors but may offer possible predictions of the probability of higher or lower recruitment in the short term. The applicability of the drift indices is adaptable in all world oceans and all marine organisms that occupy planktonic life stages exposed to dynamic ocean currents. The study demonstrates how larval drift indices help to identify larval transport or retention to be crucial for population replenishment.
Highlights
The successful persistence of a fish population is dependent on life cycle and history closure, i.e., connectivity between each life stage, spawning adults, eggs, larvae, juveniles on nurseries and recruitment of juveniles back to the adult population (Petitgas et al, 2013)
We address three main questions: Which dispersal pattern dominates during the drift phase of Norwegian spring-spawning (NSS) herring larvae in the years between 1993 and 2016? Which dispersal patterns can be linked to the different levels of recruitment? Do and how do the larval drift indices relate with NSS herring recruitment success?
Current Fields Used for Forward and Backward Simulations
Summary
The successful persistence of a fish population is dependent on life cycle and history closure, i.e., connectivity between each life stage, spawning adults, eggs, larvae, juveniles on nurseries and recruitment of juveniles back to the adult population (Petitgas et al, 2013). Adults will migrate “up stream” of suitable juvenile nursery areas so Larval Drift Essential for Recruitment that eggs and/or larvae will be delivered to the nurseries in a suitable timeframe (Parrish et al, 1981) This window is often dictated by the development time of the early life history stages and the conditioning of a nursery area prior to the arrival of the juveniles. The second retains the offspring in the vicinity of the spawning grounds, at least for a while, and so provide an imprinting mechanism for the return to specific spawning areas (philopatry, natal fidelity) (Sinclair, 1988) Both dispersal mechanisms are assumed to benefit larval survival depending on the physical features of the location in question (Houde, 1989)
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