Kathleen M. Castro

THE CONCEPTUAL APPROACH TO LOBSTER SHELL DISEASE REVISITED

Abstract A shell disease epizootic is described for the American clawed lobster (Homarus americanus) populations in southern New England. This paper presents a conceptual model for examination of shell disease and presents evidence to support three hypotheses. Hypothesis one proposes that epizootic shell disease prevalence has increased in wild lobster populations; hypothesis two proposes that there are population-level effects of shell disease and hypothesis three explores the relationship between shell disease, and environmental and anthropogenic disturbances. This conceptual model links environmental stressors to physiological upsets and disease to population level impacts and can serve as a general model of disease in the marine environment.

Observations of Epizootic Shell Disease in American Lobsters, Homarus americanus, in Southern New England

ABSTRACT Epizootic shell disease (ESD) is an emerging disease in American lobster, Homarus americanus, in southern New England (SNE). Monitoring surveys and research projects have been able to identify the initiation of the disease and changing prevalence levels over spatial and temporal landscapes, including demography. The sudden onset of ESD during the late 1990s was centered in SNE, specifically southern Massachusetts and Rhode Island, which have continued to show sustained mediumhigh prevalence levels. Legal and sublegal lobsters are both affected and we can now show that the disease occurs in small juvenile lobsters. Severity indices show little variation over time but ovigerous females have the highest prevalence and severity. Herein, we summarize available information on ESD in SNE.

Behaviour of hatchery-reared and wild-caught 4th and 5th stage American lobsters, Homarus americanus

Abstract Behavioural deficiencies in 4th and 5th stage hatchery‐reared lobsters were examined using time budget analysis and predator trials. Hatchery‐reared 4th stage lobsters were found to behave differently than wild‐caught lobsters and differences existed between hatchery‐reared lobsters from different sources. Local hatchery‐reared 4th stage lobsters spent less time on shelter and suffered higher predator rates in laboratory trials than both wild‐caught 4th stage and lobsters reared in a hatchery in Maine. Fifth stage hatchery‐reared lobsters spent significantly more time in shelter than their wild‐caught counterparts. These differences may be attributable to the lack of development of proper predator‐avoidance behaviour and need to be understood and corrected to maximise the effect of enhancement projects.

The “100 Lobsters” Project: A Cooperative Demonstration Project for Health Assessments of Lobsters from Rhode Island

ABSTRACT The emergence of epizootic shell disease in the American lobster (Homarus americanus) has been devastating to the fishing industry in southern New England. In response, research was initiated to understand the roles of the environment, pathogens, and pollutants in the ecology and etiology of the disease. A comprehensive project was initiated in which tissues and hemolymph from 100 lobsters were collected from an endemic area of disease, Narragansett Bay, RI. The project has moved forward with the purpose of compiling, synthesizing, and propagating the findings from the “100 Lobsters” Project. The resulting tissue bank and Web-based data repository and instructional tools serve as a nascent demonstration project to both the scientific community working on this disease as well as to members of the lobster industry.

Effects of trap saturation and species interaction on the capture of Callinectes Spp. crabs in the Guayas Estuary

Abstract Catchability of Callinectes spp. crabs was examined from June through August 1987 in the Guayas Estuary, Ecuador, concentrating on aspects of saturation and interaction effects in traps. Actual versus potential catch due to saturation effects was examined using an experimental design of traps with the catch removed (fished) versus traps with the catch counted but not removed (not-fished). A significant decrease in catch in the not-fished traps was observed after 3 h in the lower estuary and after 21 h in the upper estuary. Experiments to examine intraspecific or interspecific effects on the catchability of the two Callinectes species in traps were conducted in the lower Guayas Estuary using a combination of stocked treatments. Significant differences were observed in the catch of C. toxotes in the treatments with high densities of stocked C. toxotes . The catch of C. arcuatus was not affected by stocking the traps with either species in densities tested.

EFFECTS OF MOBILE BOTTOM FISHING GEAR ON BIODIVERSITY AND HABITAT IN OFFSHORE NEW ENGLAND WATERS

Abstract Mobile fishing gear affects biodiversity and habitat in New England offshore waters through selective fishing activity, seabed disturbance, and discarding and encounter mortality. Selective fishing activity results in geographically localized impacts on habitat and more widespread impacts on biodiversity through the selective removal of specific species with a higher economic value. Seabed disturbance by fishing activity results in physical impacts related to resuspension of fine sediments and scarring of the seabed, chemical effect due to resuspension of nutrients, and biological impacts related to alteration of the benthic community structure. Discards and other benthic fauna that encounter mobile gear and are impacted by the interaction, temporarily alter the ecosystem dynamic. In general, the habitat impacts are restricted to areas of heavy fishing activity, and in shallower water are ameliorated by natural processes that regularly disturb the seabed. Effects on biodiversity are more widespread due to the transient nature of many impacted species. Mobile fishing gear produces approximately 75% of the landings from New England offshore waters. Habitat impact and a loss of biodiversity may be considered a cost of seafood production. Preservation of habitat and biodiversity in marine sanctuaries and reserves is recommended to balance the effects of fishing. This is analogous to societys management strategy in the terrestrial environment.