Tropical insular fish assemblages are resilient to flood disturbance

William E Smith,Thomas J Kwak

doi:10.1890/es15-00224.1

Abstract

Periods of stable environmental conditions, favoring development of ecological communities regulated by density‐dependent processes, are interrupted by random periods of disturbance that may restructure communities. Disturbance may affect populations via habitat alteration, mortality, or displacement. We quantified fish habitat conditions, density, and movement before and after a major flood disturbance in a Caribbean island tropical river using habitat surveys, fish sampling and population estimates, radio telemetry, and passively monitored PIT tags. Native stream fish populations showed evidence of acute mortality and downstream displacement of surviving fish. All fish species were reduced in number at most life stages after the disturbance, but populations responded with recruitment and migration into vacated upstream habitats. Changes in density were uneven among size classes for most species, indicating altered size structures. Rapid recovery processes at the population level appeared to dampen effects at the assemblage level, as fish assemblage parameters (species richness and diversity) were unchanged by the flooding. The native fish assemblage appeared resilient to flood disturbance, rapidly compensating for mortality and displacement with increased recruitment and recolonization of upstream habitats.

Highlights

Many biotic interactions, such as competition and predation, are density dependent and develop as populations grow in number, while stochastic abiotic events, such as flooding and drought, periodically reset community structure and interrupt the outcome of biological interactions (Connell 1978, Jackson et al 2001)
Aquatic community structuring was framed as a dichotomy between deterministic biotic and stochastic abiotic processes as the field of stream disturbance ecology developed in the 1980s (Grossman et al 1982, 1985, Matthews 1982, Yant et al 1984)
Hurricane Irene represented an intense disturbance event in a tropical insular river, and substantial biotic effects resulted at the population level

Summary

Introduction

Many biotic interactions, such as competition and predation, are density dependent and develop as populations grow in number, while stochastic abiotic events, such as flooding and drought, periodically reset community structure and interrupt the outcome of biological interactions (Connell 1978, Jackson et al 2001). Aquatic community structuring was framed as a dichotomy between deterministic biotic and stochastic abiotic processes as the field of stream disturbance ecology developed in the 1980s (Grossman et al 1982, 1985, Matthews 1982, Yant et al 1984). Investigators of this topic reported variable stream fish assemblage structure at small scales in patchy stream habitats (Grossman et al 1982) and high assemblage stability across very large spatial scales (Matthews 1982). After years of empirical study, research findings conformed to a unifying paradigm that stream systems followed a predictable continuum from highly-disturbed, stochastically structured communities to rarely-disturbed, deterministically structured communities (Resh et al 1988, Poff and Ward 1989, Strange et al 1992)

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