Development of a Multi-Species Statistical Catch-At-Age Model for a Mid-Atlantic Species Complex: Atlantic Menhaden and Striped Bass

Predation is an often overlooked or poorly understood source of mortality, and can be the largest source of mortality for a marine fish species. Given this importance, predation is a critically important process to consider when studying the dynamics of marine fish populations. Traditionally, population models have either quantified predation externally or use a general and fixed natural mortality level. To develop a new perspective on the predation component of natural mortality, and extend recent work, a multispecies statistical catch-at-age assessment model (MSSCA) for a mid-Atlantic species complex is being developed. The initial configuration includes striped bass (Morone saxatilis) and Atlantic menhaden (Brevoortia tyrannus). Predation mortality on menhaden was modeled as a flexible function of predator and prey abundances that was fitted to stomach-content data. This initial two-species model is a proof-of-concept step; this report compares the multispecies model with a set of outputs from peer reviewed single-species models. The MSSCA model was able to successfully estimate predation of striped bass on menhaden and integrate it into a total mortality estimate, which correlated well with the existing assessment model information.