Unraveling how changing environmental conditions influence connectivity patterns in fish with ontogenetic migrations

Patrick Reis‐Santos (1,2), Susanne E. Tanner (1), Rita P. Vasconcelos (1), Bronwyn M. Gillanders (2), Henrique N. Cabral (1)

1 MARE – Marine and Environmental Sciences Centre, Faculdade de Ciências, Universidade de Lisboa, 1749‐016 Lisboa, Portugal

2 Southern Seas Ecology Laboratories, School of Biological Sciences, The University of Adelaide, SA 5005, Australia

Connectivity is a critical property of marine fish as it drives population replenishment and determines colonization patterns, and is influenced by physical, biological and ecological processes and interactions acting  over  a  range  of  spatio-temporal scales.  Understanding how  changing environmental  conditions influence dispersal and connectivity patterns is particularly important in species with ontogenetic migrations and segregated habitat use during their life history, such as marine species using estuarine nurseries. Albeit challenging, fish movement can be quantified using different methodologies. Relative contributions from estuarine nursery areas to the coastal adult populations were determined using otolith elemental composition for multiple commercially important species (Dicentrarchus labrax, Plathichthys flesus, Solea senegalensis and Solea solea) and showed high inter-annual variability. Here, the effects of environmental variation on estuarine colonization, connectivity rates and movement extent between estuarine nurseries and coastal populations are investigated using generalized linear models. Environmental conditions impacting both larval dispersal and juvenile life history stages are included in the models (e.g. wind force and direction, NAO, water temperature, river flow), as well as factors relative to estuarine colonization and nursery use (e.g. juvenile density, food availability). Environmental drivers of colonization and connectivity patterns in different fish life history stages are identified, and the implications to the development of management frameworks for ontogenetically migrating species under global change are discussed.