Abstract
While it is common knowledge that Red Drum (Sciaenops ocellatus) inhabit oligohaline waters (salinity <5), lifetime reconstructions of salinity histories have been lacking, and this study provides unique insight into interannual and ontogenetic patterns of oligohaline occupancy by this economically valuable sportfish. Growth consequences of oligohaline exposure and the relationship of oligohaline residency with river discharge were also investigated. Oligohaline exposure varied most during years 2 and 3 of life. During this time, 22% (n = 26/120 individuals) of Red Drum were oligohaline residents (≥ 90% of these years spent in oligohaline salinities), 34% (n = 41) were meso-polyhaline residents (< 10% of years 2 and 3 spent in oligohaline waters), and 44% (n = 53) spent time in both oligohaline and meso-polyhaline salinities. Trends in oligohaline residency match putative Red Drum life history. Oligohaline residents were present during years 1–6 of life; however, oligohaline residency peaked during the second year of life (n = 37, 31%) and by year 7 no oligohaline residents remained. Growth of oligohaline resident Red Drum during years 2–3 of life was lower than non-resident fish. However, long-term growth consequences of oligohaline residency were not apparent. The proportion of oligohaline residents during years 2 or 3 of life was positively related to river discharge. This divergence in salinity residency by juvenile Red Drum demonstrates that life history diversity was present in this population and that oligohaline waters provided important nursery habitat for fish that successfully recruited to the adult population.
Highlights
Life history diversity in the habitats occupied within animal populations can have important consequences for species distribution, abundance, and resilience to changing environmental conditions (Hilborn et al 2003; Kerr et al 2010; Schindler et al 2010)
The proportion of oligohaline residents during years 2 or 3 of life was positively related to river discharge. This divergence in salinity residency by juvenile Red Drum demonstrates that life history diversity was present in this population and that oligohaline waters provided important nursery habitat for fish that successfully recruited to the adult population
Red Drum habitat use and salinity exposure has previously been assessed with field surveys and tagging
Summary
Life history diversity in the habitats occupied within animal populations can have important consequences for species distribution, abundance, and resilience to changing environmental conditions (Hilborn et al 2003; Kerr et al 2010; Schindler et al 2010). Estuarine dependent fishes are typically euryhaline occupying a wide range of salinities (Able 2005) This trait may result in life history diversity in salinities that fishes inhabit throughout life and during distinct life periods, like the juvenile phase (Able 2005; Kerr et al 2009; Secor and Kerr 2009). In fishes, this diversity has been described by the population contingent hypothesis where different contingents exhibit varying migratory strategies across or residency within salinity thresholds (Clark 1968; Secor 1999; Nims and Walther 2014). Either discrete or continuous differences in estuarine habitat use and salinity exposure may be important for the resilience of populations to ongoing environmental change
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