Why and when do freshwater fish migrate? Observations of migration patterns of the native fishes from the Iberian Peninsula (SW Europe)

Abstract

We reviewed information on Iberian freshwater fish to characterize their migratory status and identify migration reasons and periods. Most species migrate (87.3 %; 62 species from 15 families). A large number are potamodromous species (45 species from 6 families) but diadromous species (17 species from 11 families) also exist, including anadromous (9 species) and cata¬dromous (8 species). The spawning period is a primary driver of fish migration but feeding and refuge-associated migrations also take place. Sexual maturity is the most important cue triggering fish migration, and other important factors include water temperature, river flow, currents, salinity and photoperiod. Spawning and migrating periods are in general prolonged and vary among years, as a response to the environmental variability of Mediterranean river systems, which are the most frequent in the Iberian Peninsula. Migratory movements of the various native species of each site cover almost the whole or the whole year. Therefore, to allow fish migration, Iberian freshwaters should always be connected, or their fish passes should be permanently, or practically always, in operation.

Spatial Study of Eel Larva Habitat in Ciletuh Bay Waters, Sukabumi Regency, West Java

“…Each fish migrates to and from the place of reproduction, which occurs annually during spawning season (Kawabata et al, 2015). External factors, such as lunar cycles, temperature, salinity, and currents, can impact the migration process (Ordeix & Casals, 2024). By analyzing these external factors, potential habitats for the abundance of migratory eel larvae can be identified.…”

The role of connectivity in conservation planning for species with obligatory interactions: Prospects for future climate scenarios

“…The ability of fish to overcome obstacles is highly dependent on their traits and life histories (Hermoso & Filipe, 2021; Table S5). Most Iberian freshwater fish species present a migratory behaviour (i.e., potamodromous or diadromous), and thus are prone to move great distances (Ordeix & Casals, 2024). As such, migratory fish species will most likely be primarily responsible for moving mussels to newly suitable habitats across the river network when compared to the few Iberian fish hosts that do not show a migratory behavior (Table S5).…”