Geology topics

Jennifer Mondragon

Publications and source records attributed to Jennifer Mondragon.

5 recordsLinked to original sources

USGS2008

Spatial patterns and movements of red king and Tanner crabs: Implications for the design of marine protected areas

Most examples of positive population responses to marine protected areas (MPAs) have been documented for tropical reef species with very small home ranges; the utility of MPAs for commercially harvested temperate species that have large movement patterns remains poorly tested. We measured the distribution and abundance of red king Paralithodes camtschaticus and Tanner Chionoecetes bairdi crabs inside and outside of MPAs in Glacier Bay National Park, Alaska, USA. By tagging a sub-sample of crabs with sonic tags, we estimated the movement of adult crabs from one of the MPAs (Muir Inlet) into the central portion of Glacier Bay where fishing still occurs. Tanner crabs and red king crabs moved similar average distances per day, although Tanner crabs had a higher transfer out of the Muir Inlet MPA into the central bay. Tanner crab movements were characterized by large variation among individual crabs, both in distance and direction traveled, while red king crabs migrated seasonally between 2 specific areas. Although Tanner crabs exhibited relatively large movements, distribution and abundance data suggest that they may be restricted at large spatial scales by habitat barriers. MPAs that are effective at protecting king and especially Tanner crab brood stock from fishing mortality will likely need to be larger than is typical of MPAs worldwide. However, by incorporating information on the seasonal movements of red king crabs and the location of habitat barriers for Tanner crabs, MPAs could likely be designed that would effectively protect adults from fishing mortality. ?? Inter-Research 2008.

Marine Ecology Progress Series↗

USGS2007

Spatial distribution of juvenile and adult female Tanner crabs (Chionoecetes bairdi) in a glacial fjord ecosystem: Implications for recruitment processes

A systematic pot survey in Glacier Bay, Alaska, was conducted to characterize the spatial distribution of juvenile and adult female Tanner crabs, and their association with depth and temperature. The information was used to infer important recruitment processes for Tanner crabs in glaciated ecosystems. High-catch areas for juvenile and adult female Tanner crabs were identified using local autocorrelation statistics. Spatial segregation by size class corresponded to features in the glacial landscape: high-catch areas for juveniles were located at the distal ends of two narrow glacial fjords, and high-catch areas for adults were located in the open waters of the central Bay. Juvenile female Tanner crabs were found at nearly all sampled depths (15–439 m) and temperatures (4–8°C), but the biggest catches were at depths <150 m where adults were scarce. Because adults may prey on or compete with juveniles, the distribution of juveniles could be influenced by the distribution of adults. Areas where adults or predators are scarce, such as glacially influenced fjords, could serve as refuges for juvenile Tanner crabs.

ICES Journal of Marine Science↗

USGS2007

The relationship between circulating ecdysteroids and chela allometry in male tanner crabs: Evidence for a terminal molt in the genus Chionoecetes

Whether male Tanner crabs, Chionoecetes bairdi, undergo a terminal molt associated with a change in claw allometry has long been debated. We measured molting hormone levels in captured male C. bairdi to assess the potential for molting. We plotted a frequency histogram of chela height to carapace width ratios and found a bimodal distribution of crabs with a ratio of approximately 0.18 separating the two modes. Male crabs with a ratio less than 0.18 were classified as "small-clawed" (SC) while crabs with a ratio greater than 0.18 were classified as "large-clawed" (LC). Circulating molting hormones between SC and LC crabs were compared. Significantly lower ecdysteroid levels were found in LC crabs, indicating that this morphotype had negligible potential for molting. Circulating ecdysteroids were measured in SC males of different shell conditions (soft, new, old, and very old) and no significant differences were found. This research suggests that the molt to LC morphology is a terminal molt. The results from this study have important implications for fisheries management because sub-legal LC males will not recruit into the fishery and removal of larger males may have long term effects on population size structure.

Journal of Crustacean Biology↗

USGS2004

Seafloor habitat mapping and classification in Glacier Bay, Alaska: Phase 1 & 2 1996-2004

Glacier Bay is a diverse fjord ecosystem with multiple sills, numerous tidewater glaciers and a highly complex oceanographic system. The Bay was completely glaciated prior to the 1700’s and subsequently experienced the fastest glacial retreat recorded in historical times. Currently, some of the highest sedimentation rates ever observed occur in the Bay, along with rapid uplift (up to 2.5 cm/year) due to a combination of plate tectonics and isostatic rebound. Glacier Bay is the second deepest fjord in Alaska, with depths over 500 meters. This variety of physical processes and bathymetry creates many diverse habitats within a relatively small area (1,255 km 2 ). Habitat can be defined as the locality, including resources and environmental conditions, occupied by a species or population of organisms (Morrison et al 1992). Mapping and characterization of benthic habitat is crucial to an understanding of marine species and can serve a variety of purposes including: understanding species distributions and improving stock assessments, designing special management areas and marine protected areas, monitoring and protecting important habitats, and assessing habitat change due to natural or human impacts. In 1996, Congress recognized the importance of understanding benthic habitat for fisheries management by reauthorizing the Magnuson-Stevens Fishery Conservation and Management Act and amending it with the Sustainable Fisheries Act (SFA). This amendment emphasizes the importance of habitat protection to healthy fisheries and requires identification of essential fish habitat in management decisions. Recently, the National Park Service’s Ocean Stewardship Strategy identified the creation of benthic habitat maps and sediment maps as crucial components to complete basic ocean park resource inventories (Davis 2003). Glacier Bay National Park managers currently have very limited knowledge about the bathymetry, sediment types, and various marine habitats of ecological importance in the Park. Ocean floor bathymetry and sediment type are the building blocks of marine communities. Bottom type and shape affects the kinds of benthic communities that develop in a particular environment as well as the oceanographic conditions that communities are subject to. Accurate mapping of the ocean floor is essential for park manager’s understanding of existing marine communities and will be important in assessing human induced changes (e.g., vessel traffic and commercial fishing), biological change (e.g., rapid sea otter recolonization), and geological processes of change (e.g., deglaciation). Information on animal-habitat relationships, particularly within a marine reserve framework, will be valuable to agencies making decisions about critical habitats, marine reserve design, as well as fishery management. Identification and mapping of benthic habitat provides National Park Service mangers with tools to increase the effectiveness of resource management. The primary objective of this project is to investigate the geological characteristics of the biological habitats of halibut, Dungeness crab, king crab, and Tanner crab within Glacier Bay National Park. Additionally, habitat classification of shallow water regions of Glacier Bay will provide crucial information on the relationship between benthic habitat features and the abundance of benthic prey items for a variety of marine predators, including sea ducks, the rapidly increasing population of sea otters, and other marine mammals.

Alaska↗

USGS2003

Living on the edge: Distribution of Dungeness crab Cancer magister in a recently deglaciated fjord

Glacier Bay, Alaska, has supported a productive Dungeness crab fishery, although the area where the fishery occurred was small relative to the remainder of the Bay. We hypothesized that 1 or more abiotic limiting factors prevented crabs from surviving in the upper Bay. We tested this hypothesis by systematically sampling for relative abundance of Dungeness crabs from the mouth to the head of the Bay. We measured salinity, temperature and turbidity at each of the sampling sites and at permanent stations to characterize the habitat within and among years. We expected to find a completely truncated spatial distribution. Instead, we found that adult Dungeness crabs can survive in habitats heavily influenced by tidewater glaciers. There were significantly fewer crabs in the upper Bay and a sharp decrease in abundance around 40 km from the mouth of the Bay. The region of the Bay beyond 40 km from the mouth had a very low density of predominately adult male crabs. The narrow size frequency distribution and the lack of small crabs is consistent with poor survival in one of the pre-adult life stages in the upper Bay.

Alaska↗