By Justin H. Lor Abstract This paper, first, gives a brief description of the anatomy and important biological characteristics of the American Lobster, Homarus americanus. It then summarizes key characteristics exhibited in their most densely populated regions of the east coast. A lens is focused on the management practices of the American Lobster fishery. The success of one of the world’s most valuable fisheries followed by a recent decline in species abundance is looked at through multiple perspectives. Resource management, climate change and general predictable changes in ecosystem variation are all analyzed to explain population rise and fall. Future implications are analyzed. In conclusion, key elements of this research are reiterated to form a compact argument to why the American Lobster Fishery is in danger of experiencing a steep decline in population numbers and resulting loss of millions of dollars in revenue. Anatomy Lobsters have a hard-outer shell known as an exoskeleton. The outer parts of the body include a tail fin, antennae, walking legs, crusher claw, pincher claw and a long narrow body segment (see Graphic 1). The blood is often clear or slightly grey and circulated though large blood vessels by a heart located behind the lobster’s stomach. On the thorax section are gills that capture oxygen from the surrounding water. Lobsters have two compound eyes on the front region of their head. The antennae are used as feelers. Lobsters also have chemosensory antennules much like the nose of a human. The crusher claw or chelipod is used for crushing prey and as such is the larger of the two claws with a rounded surface. The smaller claw is more like a knife used for manipulating the previous crushed prey into the mouth. This pincher claw is like a spike. Pereiopods line the underbelly. These features are used as walking legs and are separated into two distinct types. The pereiopods located closer to the claws have sensors almost like taste buds. The rear periods function mostly as walking legs. There are various other features and complex structures within the lobster but for this research are mostly irrelevant (Lobster Institute at The University of Maine, 2017). Habitat Homarus americanus resides along the eastern seaboard of the United State of America. Ranging from Newfoundland, Canada all the way to North Carolina, USA. The species is primarily found on the continental shelf waters shallower than 50 meters. They are sometimes found at depths up to 700 meters but this is rare. This area comprises one of the most lucrative fisheries in the US. In 2006, the fishery was estimated to be valued at $386 million. The Gulf of Maine is where most commercial catch occurs and these harvests are most successful close to shore. Spatial distribution is largely dependent on both the size and sex. Seasonal and climatic changes also affect distribution but in most cases the smaller individuals are found closer to shore where larger lobsters can be found in deeper waters. Population density distribution is also likely subject to a variety of environmental factors including the opportunity to find available shelter, specific pH and salinity range, bottom temperature, sediments, and spatial variables such as latitude and longitude (Chang et al., 2010). Fishery Management The current state of the American Lobster fishery in New England is in decline. Despite strict size requirements being implemented to ensure a healthy population and deter overfishing the population is still experiencing losses. Small sized lobsters are illegal to harvest. They are further protected by trap requirements that force lobster fisherman to install vents on all lobster traps to allow smaller lobsters the opportunity of escape. There are also other laws that further eco-regulate the impacts of lobster fishing. To reduce by-catch and harm to species other than the intended lobster further regulations are being implemented. These regulations have made being a lobster fisherman an increasingly difficult prospect but have allowed the fishery to remain vital (Morrissey et al. 2015). Records dating back to the 1800s indicate a decline in overall species number. In 2012, the fisherman harvesting from the Gulf of Maine experienced record catches. This abundance of lobster flooded the market and subsequently had an adverse effect on industry sales. With supply greater than demand the price of the lobster dropped. This drop (about $1-$2 per pound) meant large financial losses for industries selling thousands of pounds at a time. The decline in overall species number in conjunction with easier harvestability (due to technological advances and refined techniques) contributes to a steep decline in any fishery or resource management effort. New markets are continually being created and expanded to allow for fast distribution of the oversupply of lobster. Overseas vendors are taker greater interest further threatening the species (Morrissey et al., 2015). Canadian/U.S. lobstermen perception of current ocean health To enhance communication and knowledge sharing within the community of concerned lobster fisherman, a one-and-a-half-day town meeting was held in Saint John, New Brunswick on March 20 and 21. This meeting brought together people of various sectors and geographic regions connected to the American Lobster Fishery. Attendees included people from New Brunswick, Maine, Massachusetts, Prince Edward Island and Nova Scotia totaling about 65 people. Among some of their concerns were issues like changing water temperatures, ocean acidification and marine pollution. The Lobster Institute at The University of Maine (2015) reports, “The lobstermen in attendance suggested priorities should include: a cross-border effort to further advance studies on ocean acidification; training in quality control for all handlers beyond the boat, and several others” (p. 3). Among the attendees of this Lobstermen town meeting was Maine State Senator Chris Johnson who cited findings by the Ocean Acidification Commission. This commission, co-chaired by Senator Johnson, recommends monitoring acidity changes more aggressively and increased study on the impacts of ocean acidification on species like lobster. He also stated that Maine will call for a $3 million bond referendum to carry out these proposed management efforts. (Lobster Institute at The University of Maine, 2015). Potential threats Climate change and the resulting ocean acidification is an obvious threat to efforts to the American Lobster Fishery. With so many changes forecasted as a result of the warming of Earths Ocean and atmosphere the lobster is among the many threatened species. Shell forming species like lobster are threatened from ocean acidification but this is only one of the changes that will challenge their survival. As noted earlier in this report the Lobster ecosystem is comprised of various elements that need to remain in balance for their continued survival. Things like pH, temperature and salinity are sure to change as global ice caps melt and sea levels rise and warm. Future Implications Countless fisherman lives will be among the many people impacted by the downfall of the American Lobster Fishery. With many efforts by fisherman, senators and concerned scientists and citizens the potential to sustain the Homarus americanus is possible but great threats loom in the wake of an unstable global system. Millions of dollars in resource value is likely to degrade. The lobster has proven to be a hardy survivor and great resource for hundreds of years though so hopefully the changes will not be too drastic. Importance This report draws from multiple sources to connect various reports with a common interest of many millions of people. The American Lobster has been an iconic species and a trophy to many. It even appears in art and folklore for many cultures (The Lobster Conservancy, 2004). In my life and many others, it has served as a centerpiece at lavish dinners and family gatherings. This hardy crustacean has proven itself to be one of the most valuable resources in the US. Lobster, to many, is a delicacy and is sought after from far reaches. It will be a great economic loss if the management of this vital resource fails. There are many good things being done to sustain the population but climate change seems to cast a large shadow over these efforts. Summary In conclusion of this report I propose that the American Lobster Fishery is in great danger of experiencing a steep decline. There are many great efforts to sustain the population but the vital elements of the lobster habitat are all likely to change with warming water temperature and rising sea levels. References
Chang, J.H., Chen, Y., Holland, D. & Grabowski, J. (2010). Estimating spatial distribution of American lobster Homarus americanus using habitat variables. Marine Ecology Progress Series, 2010, volume 420, 145-156. Retrieved from http://www.int-res.com/articles/meps2010/420/m420p145.pdf Morrissey, J., Sumich, J., & Pinkard-Meiser, D. (2015). Introduction to the Biology of Marine Life, Eleventh Edition. Pages 161 & 162 The Lobster Conservancy. (2004). Sustaining a thriving fishery through science and community - Lobster Biology. Retrieved from: http://www.lobsters.org/tlcbio/biology.html The University of Maine, Lobster Institute. (2015). Canadian/U.S. Lobstermen’s Town Meeting – Full Transcript. Retreived from: http://umaine.edu/lobsterinstitute/files/2015/07/Final-Transcript-2015.pdf The University of Maine, Lobster Institute. (2017). Life of the American Lobster – Anatomy & Biology. Retrieved from: http://umaine.edu/lobsterinstitute/education/life-of-the-american-lobster/anatomy-biology/
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By Aaron Tucker Litwiler The Atlantic coast salt marshes of the United States are incredibly biodiverse and are home to many unique species of flora and fauna. One such species that calls this ecosystem home is the diamondback terrapin, Malaclemys terrapin. This turtle belongs to the family Emydidae which includes many common North American turtles such as box turtles, spotted turtles, and sliders (Seidel and Ernst). However, unlike the rest of the American turtles in this family, diamondback terrapins reside in the brackish waters of North America’s eastern coastline. The diamondback terrapin can be found in salt marsh, tidal flats, and estuaries from Cape Cod, Massachusetts down to Corpus Christi, Texas (Roosenburg, Willem). These turtles are known to prefer areas of low marsh that are frequently flooded, however they can be found in deeper grass beds, bays, and other deeper bodies of water. The salt marsh habitat is characterized by saltmeadow cordgrass (Spartina alterniflora), black needle rush (Juncus romerianus), and sea oxeye (Borrichea frutescens) (ATHENS, GEORGIA). The diamondback terrapin shares this habitat with countless species of fauna including Atlantic blue crabs (Callinectes sapidus) and common marsh snail (Melampus bidentatus), both of which fall prey to the terrapin (ATHENS, GEORGIA). The diet of diamondback terrapin mostly consists of snails, crabs, and mussels; however, they have been known to feed on aquatic worms, fish, insects, and even decomposing flesh. Large, more matured terrapins typically consume larger prey such as fiddler crabs, Uca pugilator, and the aforementioned Atlantic blue crab. Young terrapins and smaller males prey on snails such as marsh periwinkles, Littoraria irrorate, and the common marsh snail (ATHENS, GEORGIA). The difference in prey size amongst mature turtles is due to sexual dimorphism. Female diamondback terrapins are considerably larger than males of the species and have broader heads and larger grinding surfaces to accommodate larger prey selection. Male terrapins reach a maximum carapace length of 5.5 inches while females can grow twice that size maxing out at 11 inches of carapace length. Female terrapins also have broader heads, shorter tails, and taller shells. The latter two characteristics are due to the reproductive requirements of female turtles (Seidel and Ernst). Despite their sexual dimorphism, all diamondback terrapins share traits that are characteristic of the species. Several variations can occur amongst the seven subspecies terrapins such as carapace shape, shape of keel knobs, head and neck markings, and shell pigmentation, however they all share the same general appearance that sets diamondback terrapins apart from other species (Seidel and Ernst). They are excellent swimmers with large, stocky hind legs and smaller forelegs. Though terrapins inhabit saline environments they do not possess flippers like their sea turtle cousins; they have webbed feet instead. These turtles are flat-bodied with a grey, keeled carapace that has light and concentric markings. The plastron of this species lacks a hinge, is yellow in color, and is connected to the carapace by a flat bridge (Seidel and Ernst). Terrapins have grey or black skin that can be accompanied by dark speckling or mottling. Terrapins have adapted to the saline environment due to their development of lachrymal salt glands that help the turtles to expel salt (Gosse). Male terrapins have longer tails in order to grasp the female during mating as well as to accommodate presence of larger reproductive organs within their cloaca. Diamondback terrapins are oviparous, meaning the females must carry and lay their eggs before hatching. Consequently, females are larger in both carapace length and depth in order to accommodate a full clutch of eggs. Females lay their eggs in open, dry, sandy soil where they deposit anywhere between four to twenty-three eggs. Females can produce up to three clutches of eggs between early spring and late summer, however, they return to the same beach every year to lay (National Aquarium). The sex of the clutch is determined by the temperature at which they are incubated, much like sea turtles. The survivorship of the hatchling turtles is affected by factors such as the microclimate of the nesting area as well as the turtles’ energy store and nest predation (Seidel and Ernst). As a consequence of these, nest survivorship is typically between one and three percent. Raccoons are the primary consumer of turtle eggs, and are a large threat to their population. Raccoons are very tolerant of human development, and even flourish in developed habitat. These human developments are a threat to all brackish and saltwater turtles. The development of shorelines decreases breeding grounds for turtles along with the erosion control that is put to use. Bulkheads block turtles from accessing the dry sand, and the grasses that are planted tangle hatchling turtles and penetrate eggs. Crab pots have also been known to kill turtles by attracting curious turtles and trapping them underwater until they drown (Roosenburg, Willem) . Considering these threats to the diamondback terrapin, it is not hard to understand why they are threatened throughout much of their range. However, there is much that can be done to prevent the extinction of these turtles. Conservation efforts such as nest site protection, education of coastal communities, habitat protection, and crab pot restriction can increase the odds of survival of this incredible species (Roosenburg, Willem). Citations
Gosse, Andrew M. “Diamondback Terrapin (Malaclemys terrapin).” Savannah River Ecology Laboratory, University of Georgia, srelherp.uga.edu/turtles/malter.htm. Seidel, Michael E., and Carl H. Ernst. "A systematic review of the turtle family Emydidae." Vertebrate Zoology 67.1 (2017): 1-122. ATHENS, GEORGIA. Home range, habitat selection, and diet of the diamondback terrapin (Malaclemys terrapin) in a North Carolina estuary. Diss. The University of Georgia, 1998. Roosenburg, Willem M. "The diamondback terrapin: population dynamics, habitat requirements, and opportunities for conservation." New Perspectives in the Chesapeake System: A Research and Management Partnership. Proceedings of a Conference. CRC Publ. No. 137. 1991. “Diamondback Terrapin ( Malaclemys Terrapin).” National Aquarium, National Aquarium, aqua.org/explore/animals/diamondback-terrapin |
Biology of the Sea
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