Author: Toni L. MizerekPublisher:
ISBN:
Category :
Languages : en
Pages : 94
Book Description
The Effects of Harvesting and Habitat Fragmentation on Blue Crab (Callinectes Sapidus) Population Dynamics in Chesapeake Bay
Author: Toni L. MizerekStock Assessment of Chesapeake Bay Blue Crab (Callinectes Sapidus)
Author: A Field Study of the Population Dynamics of the Blue Crab, Callinectes Sapidus, in the Chesapeake Bay
Author: Chesapeake Biological LaboratoryPublisher:
ISBN:
Category : Blue crab
Languages : en
Pages : 30
Book Description
Synopsis of Biological Data on the Blue Crab, Callinectes Sapidus Rathbun
Author: Mark R. MillikinPublisher:
ISBN:
Category : Blue crab
Languages : en
Pages : 324
Book Description
A Field Study of the Population Dynamics of the Blue Crab, Callinectes Sapidus Rathbun, in the Chesapeake Bay
Author: Marcel M. MontanePublisher:
ISBN:
Category : Callinectes
Languages : en
Pages :
Book Description
A Field Study of the Population Dynamics of the Blue Crab, Callinectes Sapidus Rathbun, Chesapeake Bay
Author: Juvenile Blue Crab (Callinectes Sapidus) Response to Altered Nursery Habitat
Author: Megan WoodPublisher:
ISBN:
Category : Blue crab
Languages : en
Pages : 127
Book Description
Habitats of Chesapeake Bay have been altered due to anthropogenic impacts and climate change. Due to these human disturbances, seagrasses have been extirpated from many areas in lower Chesapeake Bay and persisting beds face future losses as water temperatures continue to rise. Further loss of seagrass habitat will negatively impact juvenile blue crabs (Callinectes sapidus) that use seagrass beds as nursery grounds. Habitat degradation allows for more successful introductions of exotic species, and the communities formed from the mixing of native and exotic species are known as emerging ecosystems. Gracilaria vermiculophylla, an exotic macroalga, may be an emerging nursery habitat for juvenile blue crabs in Chesapeake Bay; however the extent to which the alga is present and used as a nursery by juvenile blue crabs are largely unknown. I investigated algal distribution in the shallow littoral areas of the York River, a subestuary of Chesapeake Bay, over two years (2013 – 2014) and found that G. vermiculophylla presence correlated with salinity and that algal presence and biomass increased with seagrass presence, although biomass was generally low. The alga was present in areas where seagrasses have been lost, and is therefore likely providing nursery habitat in these areas of high megalopal recruitment. Benthic epifaunal communities had lower species richness and were less abundant in G. vermiculophylla relative to seagrass, while benthic infaunal communities had lower species richness but similar abundance in the alga relative to seagrass. Juvenile blue crab densities were similar in the alga and seagrass, although seagrass supported about 3 times as many first and second instar crabs than G. vermiculophylla. Young juvenile blue crabs preferred seagrass, which may be due to epifaunal prey preference, and G. vermiculophylla likely represents a secondary nursery habitat. Juvenile blue crab growth rates of crabs 15 – 50 mm carapace width were similar in the alga, native seagrass, and unvegetated habitat, indicating that growth does not drive ontogenetic shifts in habitat use by larger (20 – 30 mm carapace width) juveniles. Similar growth rates also suggest that G. vermiculophylla performs similarly to seagrass as a nursery habitat in terms of providing resources for growth. Simulations of density-dependent migration of young juvenile blue crabs between habitat types suggest that G. vermiculophylla may mediate continued seagrass loss, at least in part. Together, these results increase our understanding of an emerging Chesapeake Bay ecosystem and the impacts that changes to nursery habitats have on the juvenile component of the blue crab population.
Fluctuations in the Abundance of the Blue Crab in Chesapeake Bay
Author: John Cleary PearsonPublisher:
ISBN:
Category : Blue crab
Languages : en
Pages : 32
Book Description
The blue crab (Callinectes sapidus Rathbun) of the Atlantic and Gulf coasts supports the largest crab fishery in the United States. Chesapeake Bay on the Atlantic coast and the estuarine waters of Louisiana on the Gulf coast now furnish 75 percent of the catch. Fluctuations in the abundance of blue crabs have occurred over the past half century in Chesapeake Bay where year-round fisheries have long been established. This report examines the nature and causes of fhese fluctuations. Several natural factors which appear to regulate the annual survival rate and the abundance of the blue crab are discussed on the basis of available knowledge.
Stage-structured Blue Crab Population Model with Fishing, Predation and Cannibalism
Author: Fangming XuPublisher:
ISBN:
Category : Blue crab
Languages : en
Pages : 21
Book Description
Blue crab is a species of crab commonly found in the waters of the western Atlantic Ocean. It is one of the most important shellfish in the Chesapeake Bay. The blue crab fishing industry has a notable impact on the local economy, and blue crabs form a key link in the Chesapeake Bay food web. Between the mid-1990s and 2004, the blue crab population dropped by two thirds. Factors such as habitat loss, harvest pressure and climate change may have contributed to the decline. However, there hasn’t been enough research on the long term dynamic equilibrium, making it difficult to explain the change of the population. In this study, a dynamic population model is built for blue crab using ordinary differential equations. Factors such as reproduction rate, cannibalism, predation rate and fishing mortality are considered, trying to predict the long term stable state under different conditions. Our conclusion is that bistable positive states are not likely to happen with biologically realistic parameter values. Also, crabs can sustain higher fishing pressure under the more realistic assumption of sigmoidal predation/cannibalism than under the constant predation/cannibalism assumption often used in stock assessment models. This model will be useful to evaluate the effects of disease, climate change and overharvesting, and thus help regulators to make appropriate policies and conserve the blue crabs in the Chesapeake Bay.
Juvenile Blue Crab Survival in Nursery Habitats
Author: Amanda Marie BromilowPublisher:
ISBN:
Category : Blue crab
Languages : en
Pages : 86
Book Description
Predator populations can have significant impacts on prey recruitment success and prey population dynamics through consumption. Young, inexperienced prey are often most vulnerable to predation due to their small size and limited evasion capabilities. To reduce the risk of predation, new recruits and young juveniles typically settle in structured nursery habitats, such as seagrass beds, which promote higher survival by acting as refuges from predators. Thus, successful recruitment to the adult portion of the population is often dependent on the availability of suitable nursery habitat. In this thesis, I used field tethering experiments and gut content analyses to assess the role of habitat, body size, finfish predation, and cannibalism on the survival of one of the most ecologically and economically important species in Chesapeake Bay: the blue crab Callinectes sapidus. In field tethering experiments, survival probability of juvenile blue crabs in York River nursery habitats (i.e. seagrass beds, sand flats) increased significantly and additively with crab size and SAV cover. Images of predation events during tethering experiments revealed cannibalism by adult blue crabs to be a major source of juvenile mortality. Gut content analyses from three field studies identified seven predators of juvenile blue crabs in lower Chesapeake Bay nursery habitats: adult blue crabs, striped bass Morone saxatilis, red drum Sciaenops ocellatus, silver perch Bairdiella chrysoura, weakfish Cynoscion regalis, Atlantic croaker Micropogonias undulatus, and oyster toadfish Opsanus tau. Using frequency of consumption and diet proportion metrics, I determined striped bass, red drum, and silver perch to be the most impactful finfish predators on juvenile mortality, in addition to cannibalism. Atlantic croaker and oyster toadfish play minor roles in juvenile mortality in Chesapeake Bay nursery habitats. The probability of juvenile crabs being present in a predator’s gut was also significantly higher in seagrass beds than in unvegetated sand flats. Food web dynamics are an important aspect of ecosystem-based fisheries management. Understanding the ecological interactions between populations, and their environment, can provide insight into natural population fluctuations of valuable fishery species such as the blue crab. This thesis demonstrated the positive effects of body size and SAV cover on juvenile crab survival, indicating the importance of seagrass nursery habitat for blue crab population dynamics in Chesapeake Bay. However, despite the predator refuge offered by SAV, high densities of predators and prey in seagrass beds resulted in greater consumption of juveniles in those habitats. Key predators of juvenile blue crabs were also identified and their relative impacts were estimated. The predator-prey relationships revealed in this thesis were integrated into a revised food web for blue crabs in Chesapeake Bay, in the hopes of informing future ecosystem-based management efforts.