Shoreline Signals: Predicting Distribution Patterns in Nearshore Fish and Invertebrate Communities

Date of Award

Fall 2025

Project Type

Thesis

Program or Major

Oceanography

Degree Name

Master of Science

First Advisor

Jennifer Dijkstra

Second Advisor

Easton White

Third Advisor

Michael Sigler

Abstract

The difficulty of sampling mobile marine fish and invertebrates in shallow, complex, and hard-bottomed coastal and marine environments has led to fisheries monitoring gaps in the nearshore despite their recognized status as Essential Fish Habitat and their vulnerability to habitat modification and degradation. To address this, densities of commercially and ecologically important marine species were determined using Remote Underwater Video Systems (RUVS) and the MaxN counting metric. In chapter one, video observations were combined with bathymetric data, seafloor terrain, substrate type, and biogenic habitat variables. Observed ecological guilds included American lobsters, Atlantic pollock, cunner, seals, and several guilds of flatfish and crabs. In the prediction of guild densities, Random Forest models, which incorporate a suite of predictor variables, outperformed the simpler inverse path distance weighting models that only accounted for local variability in guild densities. Habitat features emerged as the most important predictors for five guilds, and geographic position and seafloor characteristics each served as key predictors for three guilds. The percentage cover of kelp bed observed in the video deployments emerged as the single most influential predictor for cunner densities, which is the most common middle trophic level forage fish in the nearshore Gulf of Maine. Analysis techniques that quantified guild overlaps, such as percentage overlap of spatial distributions and Spearman rank correlation coefficients calculated from predicted mean densities, were found to serve as powerful spatial complements to traditional multivariate cluster and indicator species analyses. Overlaps between predator and prey species were demonstrated between cunner and crabs, cunner and seabirds, crabs and lobster, and pollock and seals. The identification of spatial and temporal overlaps between seals and pollock also highlighted bycatch risks between a commercial fish species and bycaught marine mammal species. Overall, this study summarizes current fine-scale distributions of guilds through the creation of several interpolation and prediction maps, illuminates guild-specific vulnerabilities to habitat modification and degradation through the discussion of the relative importance of terrain and habitat variables for guild densities, and identifies bycatch risks as well as overlaps in the distributions of predator and prey species through the exploration of guild co-occurrences. These findings are relevant to fishery conservation and management research focused upon the density, interdependence, and life history characteristics of nearshore commercially and ecologically important species.

This document is currently not available here.

Share

COinS