Physiological Ecology and Habitat Suitability: Combining Experiments , and Surveys to Inform Stock Assessments

Grace Saba, Rutgers

Abstract

Physiological ecology and habitat suitability: combining experiments and surveys to inform
stock assessments. Incorporating “habitat effects” into stock assessment models has proven difficult. There are multiple reasons. First, the scale of most habitat studies is not matched to the scale of most assessments. Generally, the habitat studies must be “scaled-up” to be appropriate. Second, most assessment models are structurally unable to include “habitat effects”. At the NEFSC, more than 15 models are used for stock assessments, but only two have the ability to directly include habitat information (Age-Structure Assessment Program [ASAP] and Stock Synthesis 3). Despite these limitations, “habitat effects” impact stock dynamics and observations of stock dynamics. Previous work with winter flounder shows that long-term warming has reduced the amount of available habitat, which has resulted in a decrease in stock productivity (Manderson 2008, Bell et al. in prep). This information was not included in the recent assessment model because the model was structurally unable to include the effect. We are currently working to include these “habitat effects” in ASAP. “Habitat effects” also impact observations of stock abundance. Recently, we presented an analysis at the butterfish assessment that calculated the proportion of habitat sampled by a fishery-independent survey. This proportion was calculated annually based on a habitat
suitability model that was coupled with a circulation model hindcast (Figure 1). The time varying proportion of habitat sampled was then included in the assessment model as contributing to changes in catchability (Manderson et al. in prep). The habitat suitability model used in this assessment was parameterized using catch densities and temperatures from multiple field surveys. However, extracting niche dimensions from field survey collections can problematic.

Another approach is to develop niche dimensions experimentally.Physiological ecology
proposes that distribution and productivity are largely governed by metabolic responses
(Kingslover 2008). By extension, field-based habitat suitability models should compare well
with experimentally-based metabolic functions (Bozinovic et al., 2011, Sanchez Fernandez, 2012). Here we will test this premise and compare habitat suitability models based on field and experimental data. We will then evaluate the effect of parameterization on catchability estimates for butterfish along the U.S. east coast in the context of the stock assessment model.