Information needs for assessing critical habitat of freshwater fish

Abstract

The core assumptions of critical habitat designation are a positive relationship between habitat and population size and that a minimum habitat area is required to meet a recovery target. Effects of habitat on population limitation scale from (i) effects on performance of individuals (growth, survival, fecundity) within a life history stage, to (ii) limitation of populations by habitats associated with specific life history stages, and (iii) larger-scale habitat structure required for metapopulation persistence. The minimum subset of habitats required to achieve a recovery target will depend on the extent, quality, and spatial configuration of habitats available to sequential life history stages. Although populations may be limited by available habitat for a single life history stage, altering habitat quality for subsequent stages will also affect individual survival and population size, providing multiple leverage points within a life history for habitat management to achieve recovery targets. When habitat-explicit demographic data are lacking, consequences of uncertainty in critical habitat assessment need to be explicit, and research should focus on identifying habitats most likely to be limiting based on species biology. Résumé :Les présuppositions fondamentales qui sous-tendent la désignation des habitats critiques sont l'existence d'une relation positive entre l'habitat et la taille de la population et la nécessité d'un habitat minimal afin de pouvoir atteindre un objectif de récupération. À différentes échelles, les effets de l'habitat sur la limitation des populations vont (i) d'effets sur la performance individuelle (croissance, survie, fécondité) pendant une étape particulière du cycle, à (ii) la limitation des populations par des habitats spécifiques à certaines étapes du cycle et finalement à (iii) la néces-sité d'une structure d'habitat à plus grande échelle pour la persistance de la métapopulation. Le sous-ensemble minimal d'habitats requis pour atteindre un objectif de récupération va dépendre de l'étendue, de la qualité et de la configuration spatiale des habitats disponibles aux étapes successives du cycle. Bien que les populations puissent être limitées par la disponibilité d'habitats à une seule étape de leur cycle, une modification de la qualité de l'habitat pour les éta-pes subséquentes affectera aussi la survie individuelle et la taille de la population, ce qui fournit de multiples points d'intervention au cours d'un cycle biologique pour atteindre les objectifs de récupération par l'aménagement des habitats. Lorsqu'il n'existe pas de données démographiques spécifiques aux habitats, il faut que les conséquences de l'incertitude dans l'évaluation des habitats critiques soit explicite; la recherche devrait alors se concentrer sur l'identification des habitats qui sont les plus susceptibles d'être limitants d'après la biologie de l'espèce.[Traduit par la Rédaction] Rosenfeld and Hatfield 698

A Long-Term Study of Ecological Impacts of River Channelization on the Population of an Endangered Fish: Lessons Learned for Assessment and Restoration

“…Assessing impact magnitude or restoration success both require teasing environmental signals from the background noise of the spatiotemporal variation exhibited by real ecosystems [17]. The scope (spatial extent and temporal duration) of habitat use by focal species must be acknowledged so all relevant life stages are considered [18,19]. Detecting relevant signals requires paying attention to the spatiotemporal design of monitoring protocols and the selection of ecological indicators to be monitored.…”

A geomorphic assessment to inform strategic stream restoration planning in the Middle Fork John Day Watershed, Oregon, USA

“…In a case such as this, restoration priorities set by in-channel features alone are likely to be misleading. Further, a watershed-scale perspective on the abundance and spatial arrangement of particular reach types -some of which may be rare but critical to particular species and/or life stages -is needed to understand the overall feasibility of watersheds to support robust and resilient fish populations (Fausch et al, 2002;Rosenfeld & Hatfield, 2006). Yet, fish population and habitat assessments have historically neglected this critical multi-scale view (Fausch et al, 2002).…”

Using a continuous riverscape survey to examine the effects of the spatial structure of functional habitats on fish distribution

“…Identifying and protecting these patches is often a key criterion in conservation plans (Rosenfeld & Hatfield 2006). However, the (often overlooked) spatial structure of these functional habitat patches is also important, as it indicates whether fish with certain movement characteristics are likely to use the different habitats (Schlosser 1995).…”

“…In another study looking at steelhead trout (Oncorhynchus mykiss), the distribution of spawning sites was more easily predicted by examining their 'ecological neighborhood' (Falke et al 2013). Elsewhere, the concept of complementation, while not explicitly mentioned, can be seen in studies where the importance of habitat configuration is recognized, especially in restoration strategy (Pedroli et al 2002;Rosenfeld & Hatfield 2006). Another research project examined the role of the proximity of two different habitats for rosyside dace (Clinostomus funduloides, Freeman & Grossman 1993).…”

“…Dealing with complex life histories and complementary resources has been identified as a challenge when incorporating the question of connectivity into riverine fish ecology (Fullerton et al 2010). According to Rosenfeld and Hatfield (2006), the most appropriate spatial metrics to examine functional habitat availability and connectivity have yet to be identified. They can change depending on species, life stage, season, and the characteristics of a given river.…”