Temporal patterns of the catadromous thinlip grey mullet migration in freshwater

Abstract

The thinlip grey mullet (Chelon ramada Risso, 1827) is a catadromous fish that performs massive migrations to freshwater habitats for feeding purposes that can assume a structuring role on riverine ecology due to the biomass involved in these movements. Seasonal movements of thinlip grey mullet through a vertical slot fish pass located in River Mondego (Portugal) were continuously monitored between 2013 and 2017. The extent of trophic migration, population size structure, biomass and the environmental triggers of bi-directional species' migratory activity were analysed. Between March and November of 2013/2014, $2 million and 1 million movements were respectively recorded. From a subsampling approach, the upstream movements between 2015 and 2017 were estimated. Annually, around five hundred thousand upstream movements can occur to provide species access to the upstream freshwater reaches. Movements are exclusively diurnal, and the population composed by young adults in their first year of maturity, yet juveniles and larger fish were present (TL range: 90-540 mm). Upstream movements increased with temperatures above 15 C, reaching a peak at around 20 C coupled with a photoperiod of 15 h. Downstream movements attained the higher rates when temperature dropped from 22 C to 20 C and photoperiod to 13 h. However, under wetter hydrological conditions (as in 2014), discharge flows have a higher influence.These finding provide unique information regarding species migration to freshwater habitats in the Atlantic coast, namely the extended periods spent in such environments, overlapping with the spawning migration period. Additionally, highlights the importance of species' trophic migration both for its life cycle and riverine food-web.

Do catadromous thinlip grey mullet benefit from shifting to freshwater? A perspective from fatty acid signature analysis

“…1 ). In freshwater, the animals were trapped inside a fish pass (Coimbra Dam, Pereira et al 2021 ). Summer sampling was performed with a time lag between the estuarine and freshwater environments to reduce the potential pre-spawning mixture of both profiles in the estuary.…”

“…However, the role of different migratory behaviors and breeding strategies in fish metabolism and the lipid reserves’ quantity and quality remain poorly studied (Capoccioni et al 2018 ; Ramos-Júdez et al 2023 ), particularly among species with lower economic value, such as the catadromous thinlip grey mullet ( Chelon ramada Risso, 1827). A highly abundant species distributed along the Northeastern Atlantic, the Mediterranean, and the Black Sea (Turan 2016 ) that spawn in the sea and undergo a somatic growth period that can occur in the estuary or often, but not always, in freshwater environment (Almeida 1996 ; McDowall 1997 ; Pereira et al 2021 ).…”

“…In the Atlantic region, a fraction of the C. ramada population is known to perform an extensive trophic migration to freshwater, which usually starts in March and can extend until November (Pereira et al 2021 ). During this period of somatic growth, this euryhaline species shows a high osmoregulatory capacity and feeding plasticity (specialized feeding apparatus) that provide them a unique ability to exploit spatially variable resources (Lebreton et al 2011 ; Cardona 2016 ; Carassou et al 2017 ).…”

Assessment of wastewater-borne pharmaceuticals in tissues and body fluids from riverine fish

“…Ebro barbel and common carp are benthic omnivore that stirs the bottom to feed (García-Berthou, 2001;Benejam et al, 2009). The thinlip mullet is a catadromous fish that migrates to freshwater habitats for feeding purposes, where extended periods are spent in such environments (Pereira et al, 2021). Adults of thinlip mullet feed on epiphytic algae, detritus, small benthic or planktonic organisms, pelagic eggs and larvae (Freyhof & Kottelat, 2007).…”

The decline of the ecosystem services generated by anadromous fish in the Iberian Peninsula

“…Climate change is a growing threat to anadromous fishes that have complex interactions and cumulative effects with other threats (e.g., Maitland et al, 2015;Clemens et al, 2021), and Iberia is located in a region particularly vulnerable to this threat (e.g., Andrade et al, 2021;Pereira et al, 2021). Physical changes in temperature, precipitation, groundwater discharge, and increased ice-free periods for lakes could affect community structure and the fecundity, survival, growth, and distribution of anadromous species (Hittle et al, 2021).…”