Shellfish Aquaculture Glossary of Terms:


Algae: non-vascular plants that grow submerged in marine or freshwater environments. Large bodied algae, such as rockweed or sea lettuce, are called macroalgae. Single-celled algae floating in the water and providing food for shellfish are called phytoplankton.


Ambient: pertaining to the status of the surrounding environment. For example, abmbient temperature describes the natural temperature of the water or sediment in which the clam exists.


Anoxia: a situation where the amount of dissolved oxygen in the water is reduced to zero. The end result is a localized area that is not capable of supporting biological activity.


Anthropogenic: derived from or associated with human activity, often used to describe environmental contamination resulting from human activities.


Biodiversity: a description of the variety, abundance and distribution of living organisms within a defined ecosystem or habitat.


Biofouling: the overgrowth or alage, marine invertebrates, and other organisms on nets, intake pipes, and structures in the water. Biofouling can restrict water flow and access to oxygen and food by the growing shellfish.


Breeding selection: a strategy applied to domesticated plants and animals where the genetic traits controlling specified and desirable qualities of the organism are preserved and amplified through conventional reproductive pairings of parent stock. A technique commonly used at shellfish hatcheries.


Broodstock: those adult organisms that are held and used a parent stock for controlled breeding within a hatchery.


Crash: a situation where a dense population of an organism, e.g. a bloom of phytoplankton, depletes the resources from their immediate environment that are necessary to support their life processes. This results in the population, as a whole, dying within a short time interval.


Denitrification: a chemical process that is mediated by bacteria in the sediment and that converts organic nitrogen (in the form of ammonia, nitrite, and nitrate) to elemental nitrogen (in the form of nitrogen gas).


Direct transmission: a disease pathogen that is capable of infecting its host organism directly from a previous host of the same species.


Dissolved oxygen: in the aquatic environment , the life supporting gas oxygen  is present dissolved in solution with the water and must be extracted from the water by living organisms using specialized respiratory structures, such as gills. If the level of dissolved oxygen drops too low, then respiratory distress leading to death may occur.


Eutrophication: an environmental condition where excess nutrients, in the form of nitrogen, are introduced into a water body leading to increase growth of micro and macroalgae.


Facultative: a disease-causing organism that is capable of living outside of their host in the marine environment.


Fecal coliform bacteria: a class of bacteria that is unique to the intestinal tracts of warm-blooded animals and is used as an indicator of the presence of human waste in the aquatic environment.


Genetic diversity: the variety of genetic materials within a single species of organism that permit the organism to adapt to changes in the environment.


Hard Clam: another name for quahog. On Cape Cod we never say "hard clam" because it instantly identifies you as a wash ashore and maybe even a New Yorker. Ugh! We are Red Sox Nation. We do not consume Manhattan clam chowder. Only maybe a few manhattans once in a while and always quahog chowder.


Health inspection certificate: a document provided by a shellfish pathologist that demonstrates a specific group of shellfish have been analyzed for all known pathogenic organisms and that reports on the shellfish health status resulting from the inspection.


Hypernutrification: a situation where excess nutrients, primarily nitrogen, are introduced into the aquatic environment resulting in eutrophication.


Hypoxia: a situation where the amount of dissolved oxygen in the water is reduced to a level significantly lower than its theoretical maximum resulting in induced stress in aquatic organisms due to lack of oxygen for normal metabolism.


Indirect transmission: a disease pathogen that is not capable of infecting its host organism directly from a previous host of the same species but rather it must pass through an alternate host before becoming infective to the target organism.


Infauna: those aquatic organisms that exist buried in the sediment as opposed to those that live at the sediment surface or in the water column.


Juvenile clam: a size class of clam defined as the interval between metamorphosis (set) and when the animal becomes sexually mature or attains a marketable size.


Littleneck: one of a number of marketing names for the quahog, Mercenaria mercenaria. The littleneck represents a sub-adult quahog in the size range of approximately 2 inches in length up to 2.5 inches.


Macroalgae: a classification of algae that are defined according to the size of the plant where the body of the plant is large enough to be observable to the eye.


Microalgae: a classification of algae that are defined according to the size of the plant where the body of the plant is small enough that it requires magnification to observe.


Mollusk: a member of the Phylum Mollusca.


Mortality rate: the rate at which a population or organisms are dying due to adverse environmental conditions, a disease situation or some other stress impacting the population.


Nursery: a practice conducted by shellfish farmers where very small shellfish are held under conditions that promote growth while protecting them from predators and other environmental hazards. Generally this intermediary culture step grows the shellfish from post-metamorphosis (post-set) to size large enough to be held in the grow-out system or directly seeded.


Nutrients: a variety of chemical compounds that are necessary to promote growth of plants and animals. In the marine environment, the most common nutrient that is limiting for plant growth is nitrogen in the form of nitrate (NO3-).


Obligate: a disease-causing organism that cannot live in the marine environment on its own and must reside in the host tissue to survive.


Oyster: Crassostrea virginica, a commercially important bivalve mollusk native to Massachusetts. Also known as the American oyster.


Pandemic: a situation where a disease organism is commonly found in the local environment and presence of the disease in local populations of the host organism is routinely observed.


Pathogen: any type of biological entity that causes disease through infecting a host organism.


Phytoplankton: small single-celled algae that are commonly found suspended in the water column and provide the first step in the food chain of an aquatic system.


Quahog: Mercenaria mercenaria, a commercially important bivalve mollusk native to Massachusetts. Also known as the hard clam, littleneck, cherrystone, and chowder clam.


Salinity: a measurement of the amount of salt that is dissolved in water and is normally reported in parts per thousand (ppt).? Normal seawater has a salinity of 30-35 ppt.


Scallop: a family of commercially important bivalve mollusks. Those native to Massachusetts include the bay scallop (Argopecten irradians) and the sea scallop (Placopecten magellanicus). Cape Codders call these "SKOL-LOPS" and never "scale-lups" as they do on those Red Lobster commercials on TV. You'd thing those ad guys would get it right!


Sediment: any material having a geological origin and comprised of small particles. The size of the individual particles determines the description of the sediment and it can range from fine clay to coarse gravel.


Sedimentation: a situation where sediment is moved by wind or waves from one area to another and in the course of that movement may bury or block structures or organisms in the path of the sediment movement.


Seed clam: a stage in the growth of a shellfish that is generally demarcated by size and the culture system that it is derived from. Seed clams are generally small and are derived from a nursery culture system.


Siphon: the part of the clam?s anatomy that provides a channel for the seawater to enter and leave the mollusks body cavity that houses the gills, the digestive system and the feeding apparatus.? Sometimes referred to as the neck.


Submerged aquatic vegetation (SAV): any of a group of vascular plants that can live and grow under water. Local examples of submerged aquatic vegetation include eelgrass (Zostra marina) and widgeon grass (Ruppia ruppia).


Wet storage: a practice where harvested shellfish are held in seawater during the interval between harvest and consumption.


Wetlands buffer zone: naturally vegetated resource areas defined to provide protection of wetland areas from man-made alterations of the upland adjacent to the wetlands.


* Excerpt from Best Management Practices for the Shellfish Culture Industry in Southeastern Massachusetts, SEMAC