Cause and consequences of Common Snook (Centropomus undecimalis) space use specialization in a subtropical riverscape

Abstract

Variability in space use among conspecifics can emerge from foraging strategies that track available resources, especially in riverscapes that promote high synchrony between prey pulses and consumers. Projected changes in riverscape hydrological regimes due to water management and climate change accentuate the need to understand the natural variability in animal space use and its implications for population dynamics and ecosystem function. Here, we used long-term tracking of Common Snook (Centropomus undecimalis) movement and trophic dynamics in the Shark River, Everglades National Park from 2012 to 2023 to test how specialization in the space use of individuals (i.e., E_adj) changes seasonally, how it is influenced by yearly hydrological conditions, and its relationship to the between individual trophic niche. Snook exhibited seasonal variability in space use, with maximum individual specialization (high dissimilarity) in the wet season. The degree of individual specialization increased over the years in association with greater marsh flooding duration, which produced important subsidies. Also, there were threshold responses of individual space use specialization as a function of floodplain conditions. Greater specialization in space use results in a decrease in snook trophic niche size. These results show how hydrological regimes in riverscapes influence individual specialization of resource use (both space and prey), providing insight into how forecasted hydroclimatic scenarios may shape habitat selection processes and the trophic dynamics of mobile consumers.

Keywords: Acoustic telemetry; Everglades; Habitat use similarity; Movement ecology; Trophic niche.

Fig. 1

Map of Shark River, Everglades National Park (ENP). Panel (a) depicts the boundaries of ENP and the Shark River (solid black lines) in southern Florida. Panel (b) shows the boundaries of each river zone (solid black lines), location of acoustic listening stations (i.e., acoustic receivers; black dots), and location of hydrologic monitoring station immediately upstream of the Shark River’s headwaters (black star). Map was generated using QGIS v3.22.6 (https://qgis.org/).

Fig. 2

Marginal effect plots from generalized additive models (GAMs) for temporal trends in the individual space use specialization (E_adj) of Common Snook (Centropomus undecimalis). Panel (a) depicts the intra-annual (seasonal) cycle of individual space use specialization. Panel (b) depicts the trend across the time series. Solid black lines indicate the estimated mean response, dotted black lines show the 95% confidence intervals, and grey shading illustrates the dispersion around the mean.

Fig. 3

Marginal effect plots from generalized additive models (GAMs) for hydrological effects on individual space use specialization (E_adj) of Common Snook (Centropomus undecimalis). Panel (a) depicts the relationship between mean marsh stage (cm) and individual space use specialization. Panel (b) depicts the relationship between days with mean river stage < 30 cm and individual space use specialization. Solid black lines indicate the estimated mean response, dotted black lines show the 95% confidence intervals, and grey shading illustrates the dispersion around the mean.

Fig. 4

Pearson correlation between log(trophic niche volume) and mean dry season individual space use specialization (E_adj). The grey shading illustrates 95% confidence intervals.