Modeling the Effects of Fishing and Implications for the Design of Marine Protected Areas: Juvenile Fish Responses to Variations in Seafloor Habitat

• Published in: Conservation biology Vol. 15; no. 2; pp. 424 - 437
• Main Authors: Lindholm, James B., Auster, Peter J., Ruth, Matthias, Kaufman, Les
• Format: Journal Article
• Language: English
• Published: Boston, MA, USA Blackwell Science Inc 01.04.2001; Blackwell Science; Blackwell
• Subjects: Animal, plant and microbial ecology; Applied ecology; Aquatic habitats; Biological and medical sciences; Conservation biology; Conservation, protection and management of environment and wildlife; Fisheries management; Fundamental and applied biological sciences. Psychology; Gadus morhua; Habitat conservation; Marine; Marine fishes; Mortality; Ocean floor; Parks, reserves, wildlife conservation. Endangered species: population survey and restocking; Protected areas; Wildlife habitats; Young animals; Gulf of Maine; Atlantic Ocean; North Atlantic; ANW, USA, Maine Gulf; USA, Maine Gulf; Impact study; Ocean bottom; Fishing; Modeling; Young animal; Marine environment; Conservation area; Vertebrata; Pisces; Population recruitment; Nature reserve; Selection criterion; Habitat; Gadus morhua; Environment quality; Benthic zone
• ISSN: 0888-8892; 1523-1739
• DOI: 10.1046/j.1523-1739.2001.015002424.x

A number of recent studies have linked post-settlement survivorship of Atlantic cod (Gadus morhua) with the complexity of the seafloor to which fish settle. Survivorship is greater in habitats of higher complexity (e.g., pebble-cobble substratum with emergent epifauna > pebble-cobble > sand), where cover provides shelter from predators. Fishing with mobile gear such as bottom trawls and dredges reduces the complexity of seafloor habitats. We used a dynamic model to (1) link patterns in habitat-mediated survivorship of post-settlement juvenile cod with spatial variations in habitat complexity, (2) simulate habitat change based on fishing activities, and (3) determine the role of marine protected areas in enhancing recruitment success. Density-dependent natural mortality was specified as three alternative functional response curves to assess the influence of different predator foraging strategies on juvenile survivorship during the first 12 months of demersal existence. We applied the model to a theoretical patch of hard-bottom substrata and to a case study based on seafloor habitat distributions at Stellwagen Bank National Marine Sanctuary (Gulf of Maine, Northwest Atlantic). Our results demonstrate that patterns in the shape of response surfaces that show the relationship between juvenile cod survivorship and density as well as movement rate were similar regardless of functional response type, that juvenile cod movement rates and post-settlement density were critical for predicting the effects of marine protected-area size on survivorship, and that habitat change caused by fishing has significant negative effects on juvenile cod survivorship and use of marine protected areas can ameliorate such effects.