Patterns and consequences of life history diversity in salinity exposure of an estuarine dependent fish

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.

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