Population Dynamics of an Estuarine-Dependent Fish, the Spot (Leiostomus xanthurus), ASong a Tidal Creek–Seagrass Meadow Coenocline

Abstract

To study the population dynamics of young-of-the-year spot (Leiostomus xanthurus) I released 6981 marked fish midway up the tidal creek portion of a small (<20 ha) marsh creek–seagrass meadow coenocline. Holding mortality experiments (96 h) indicated that 61.5%, or 4300 individuals, survived the marking process to constitute the population available for recapture. Over a 90-d study period, 212 marked fishes were recaptured. From plots of the ratio of marked to unmarked individuals in subsequent samples, I concluded that the population was resident in the creek for up to 182 d with the average individual present for 91 d. When this population turnover rate was compared to the total population decay rate (marked plus unmarked fish), the exchange between habitats (immigration/emigration) accounted for about 26% of the total decay rate, with the remainder attributed to natural mortality. By correcting the overall disappearance rate for population turnover due to immigration/emigration, and using this adjusted value as a measure of instantaneous mortality (Z), the estimated production in this population was 21.8 kcal (91342 J)∙m−2∙d−1. This figure is over six times greater than previously reported values for this species for all size classes over the entire growing season.