PARENT SESSION
Oral Session # 28: Ecological Modeling II.
Presiding: R Park
Tuesday, August 5. 1:30 PM to 5:00 PM, SITCC Meeting Room 102.
Dynamic behavior modeling of within-river patch selection of striped bass along the Massachusetts coast.
FINN, JOHN*,1, MATHER, MARTHA1, FERRY, KRISTEN2, 1 Universtiy of Massachusetts, Amherst, MA, 010032 Massachusetts Division of Marine Fisheries, Gloucester, MA, 01930
ABSTRACT- Striped bass (Morone saxatilis) are opportunistic generalists that utilize a wide range of habitats and prey in coastal rivers throughout the summer. Where fish occur in the river, and how long they stay, may depend on the relative energetic profitability of within-river habitats. We developed a dynamic-programming, patch-selection model and tested which of the within-river habitat patches maximize growth, given patch-specific temperature and prey conditions. Striped bass were modeled as two state variables: gut contents and weight. Each estuary was modeled as seven patches: salt marsh tidal creeks (3), estuary proper (3), and near shore ocean. Within each patch, striped bass can choose one of 10 behaviors: 'safe' behavior, 3 sit and wait feeding behaviors , 3 searching feeding behaviors and 3 movement behaviors . We analyzed conditions in 3 rivers over 3 seasons. The model runs in 10 minute steps over a single daylight portion of a tidal cycle. Results vary over the weight and stomach contents of the striped bass, and over rivers and seasons. For example, in spring ebb tide, bass starting in the upper estuary stayed and fed by sitting and waiting for fish. Bass in the lower estuary and ocean stayed put and searched for invertebrates. Fish in the rest of the patches moved downstream until they reached one of the above patches. In the spring and fall anadromous fish prey attracted striped bass to in-river habitats where the prey concentrate. Overall, the model predicts the distribution and behavior of striped bass in Mass. coastal rivers. The model predicts spatial distribution of the population, and stomach contents and movement histories of individual fish. Although parameter rich, this model incorporates realistic biological behavior and outputs a suite of variables that allow detailed model testing.
Key words: behavioral modeling, striped bass, dynamic programming, Massachusetts estuaries