Water infrastructure and the migrations of amphidromous species: impacts and research requirements

Abstract

Amphidromous species undertake a number of migrations throughout their life-history, migrating to sea immediately after hatching in freshwater, migrating back to freshwater after a pelagic larval period, and potentially undertaking adult spawning migrations. Amphidromous species are therefore likely to be highly susceptible to water infrastructure, having different migratory directions, objectives, and requirements at different life stages. We review the current state of knowledge on the migrations of amphidromous species, identifying the requirements for successful migrations, and potential threats from water infrastructure associated with anthropogenic activities. Newly hatched larvae migrating downstream are susceptible to numerous hazards associated with water infrastructure, including larval retention and starvation in freshwater, entrainment and impingement at water intakes, and barotrauma and physical damage associated with weirs and turbines. Distinct patterns of larval drift (spatial and temporal) may provide opportunities to alleviate mortality during larval emigration. While instream barriers inhibit the upstream migrations of amphidromous post-larvae and juveniles, climbing abilities are common, allowing for creative solutions facilitating upstream migration. Downstream spawning migrations are common in numerous amphidromous taxa, and are often associated with natural changes in flow regime, highlighting the need for bidirectional passage, and the potential for artificial flow alteration to negatively affect reproduction. Much research on the passage of amphidromous taxa has focussed on upstream migrating juveniles, while downstream migrating adults and larvae, which may be far more susceptible to water infrastructure, have largely been ignored. This life-stage bias represents a key research gap that must be addressed to safeguard amphidromous species in future.

Climbing for dummies: recommendation for multi‐specific fishways for the conservation of tropical eels and gobies

“…Moreover, their stochastic seasonal and diel migration dynamics limits the efficiency of water diversion shutdown (Lagarde et al ., 2018 b ). Methods to mitigate the impact of dams on the downstream migration of sicydiine (and other amphidromous species) larvae are urgently needed and this key research gap must be central in applied research concerning these species (Jarvis & Closs, 2019).…”

Water temperature influences larval survival of the amphidromous goby Sicyopterus lagocephalus

“…They are also more sensitive to stream alterations (e.g. river obstacles, water reservoirs and flows regulation) that contribute to warm the water and increase the drifting duration (Jarvis & Closs, 2019; Lagarde et al, 2018; McRae, 2007).…”

“…Immediately after hatching, the free embryos drift to the sea where the larvae develop for months before returning in rivers (Bell, 1994; McDowall, 2009). This transition between the freshwater and marine water at an early developmental stage enhances the sensitivity of these species to environmental disturbances (Jarvis & Closs, 2019; McRae, 2007; Walter et al, 2012). For example, rivers flow reduction due to water abstraction, or presence of reservoirs along the river courses, will expand the time required for individuals to reach the sea, while the water in which they drift warms up (Brasher, 2003; Jarvis & Closs, 2019).…”

“…This transition between the freshwater and marine water at an early developmental stage enhances the sensitivity of these species to environmental disturbances (Jarvis & Closs, 2019; McRae, 2007; Walter et al, 2012). For example, rivers flow reduction due to water abstraction, or presence of reservoirs along the river courses, will expand the time required for individuals to reach the sea, while the water in which they drift warms up (Brasher, 2003; Jarvis & Closs, 2019). In oceanic waters, the temperature records over the recent decades indicate a warming >0.1°C per decade in the western tropical Indian Ocean (Roxy et al, 2014).…”

Landscape biogeography and population structuring of a facultatively amphidromous galaxiid fish, Galaxias brevipinnis

“…This may be due to their strong rheotactic behaviour after hatching, which may limit dispersal from their pelagic developing environment (Hicks, 2012). Further, diadromous adults are rarely found upstream of lakes, despite the absence of any obvious in-stream barriers blocking access, possibly due to the lack of a rheotactic cue allowing juveniles to navigate through large pelagic environments (Hicks, 2012;Jarvis & Closs, 2019). Thus, populations of G. brevipinnis may potentially exhibit context-dependent degrees of population isolation and genetic structuring, creating an ideal opportunity to examine the importance and interaction of behaviour and landscape on population connectivity across temporal and spatial scales.…”