Defining essential fish habitat in an ecosystem context: practical identification and relevance to management

While traditional fisheries management has been that of a single species approach, ecosystem-based management would allow for greater confidence and efficiency in fisheries management decision making. However, there is no consensus regarding what ecosystem-based management would look like in practice. The goal of this dissertation was to create a conceptual framework that will guide the incorporation of habitat data into existing fisheries management paradigms. This framework consists of three focus areas: (1) functional examination of fisheries-habitat relationships, (2) identification of linkages from habitat to population level impacts, and (3) identification of relevant application to specific management scenarios. The Black Drum (Pogonias cromis) population in the Upper Laguna Madre (ULM) was used as a case study to exemplify the quantification of functional habitat relationships (focus area 1) and to further link stage-specific habitat relationships (e.g., nursery habitat) to the population dynamics of the full population (focus area 2). These analyses were conducted using data from fisheries independent bag seine surveys collected by Texas Parks and Wildlife Department. Relationships between habitat variables (salinity, water temperature, and dissolved oxygen) and juvenile vital rates (mortality and growth) were modeled and then employed in a stage-specific population model. The salinity – juvenile mortality relationship was found to substantially influence the finite rate of increase for the full population. Two specific application of habitat data in fisheries management decision making were then demonstrated (focus area 3). The first application used habitat suitability models for three estuarine species to examine changes in the extent and distribution of suitable habitat within three classes of estuary (positive, neutral, and negative) across three salinity regimes (low, moderate, and high). The second application was a formal decision support tool that used