Measure of a population size. The quantity of individuals in a population or in a specific area (e.g., fishing grounds) as expressed in number of fish or in biomass. Abundance can be measured in absolute or relative terms.
A management plan that acknowledges the uncertainty of a managed system and therefore integrates design, management, and monitoring in order to allow managers to adapt and to learn.
Fish that spend their adult life in the sea but swim upriver to freshwater spawning grounds in order to reproduce.
Absence of oxygen relative to atmospheric levels.
A set of reference data or analyses used for comparative purposes; it can be based on a reference year or a reference set of (standard) conditions.
A formal statistical approach in which expert knowledge or beliefs are analyzed together with data. Bayesian methods make explicit use of probability for quantifying uncertainty. Bayesian methods are particularly useful for making decision analyses.
The bottom of a waterbody; organisms that live on or in the bottom of a waterbody.
The cycling of nutrients between the bottom sediments and the overlying water column.
The total weight of a stock or population of organisms at a given point in time, usually in pounds or metric tons (2,205 pounds = 1 metric ton).
Relating to life and living organisms.
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Dynamic Changes in Marine Ecosystems: Fishing, Food Webs, and Future Options Appendix D Glossary abundance: Measure of a population size. The quantity of individuals in a population or in a specific area (e.g., fishing grounds) as expressed in number of fish or in biomass. Abundance can be measured in absolute or relative terms. adaptive management: A management plan that acknowledges the uncertainty of a managed system and therefore integrates design, management, and monitoring in order to allow managers to adapt and to learn. anadromous: Fish that spend their adult life in the sea but swim upriver to freshwater spawning grounds in order to reproduce. anoxia: Absence of oxygen relative to atmospheric levels. baseline: A set of reference data or analyses used for comparative purposes; it can be based on a reference year or a reference set of (standard) conditions. Bayesian: A formal statistical approach in which expert knowledge or beliefs are analyzed together with data. Bayesian methods make explicit use of probability for quantifying uncertainty. Bayesian methods are particularly useful for making decision analyses. benthic: The bottom of a waterbody; organisms that live on or in the bottom of a waterbody. benthic-pelagic coupling: The cycling of nutrients between the bottom sediments and the overlying water column. biomass: The total weight of a stock or population of organisms at a given point in time, usually in pounds or metric tons (2,205 pounds = 1 metric ton). biotic: Relating to life and living organisms.
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Dynamic Changes in Marine Ecosystems: Fishing, Food Webs, and Future Options bottom-up management: A process of management in which information and decisions are decentralized and in which resource users actively participate in the decision-making process. bycatch: The portion of a fishing catch that is discarded as unwanted or commercially unusable. cascading effect (or trophic cascade): A food web phenomenon in which changes in abundance at a higher trophic level lead to changes in abundance at lower trophic levels. catch: The total number (or weight) of organisms caught by fishing operations. Catch should include all organisms killed by the act of fishing, not just those landed. catch control rule: A formula used to determine the catch quota as a function of some specific indicators of stock status and any other variable condition used to adjust annual harvest targets. The control rule provides numeric guidance for adjusting catch rates to track forecasts of fluctuations in stock abundance and to achieve management goals. In many fisheries, it is the primary mechanism for regulating harvest rates. catch quota: A limit placed on the total catch allowed within a particular period of time. commercial fisheries: Harvesting fish for profit. This includes those caught for sale, barter, and trade. decadal oscillation: Cyclical changes where shifts occur on scales of roughly 10 years. degrade: To reduce in value or level. In this context, degraded is used to describe ecosystems that have been exploited to a point where there is a loss of desired uses, including a reduction in overall productivity or the loss of species. depensatory: A situation in which mortality rate increases and/or reproduction decreases as the size of the population decreases. Ecopath model: An ecological/ecosystem modeling software used to develop a static, mass-balanced representation of the feeding interactions and nutrient flows in an aquatic ecosystem. effort: The amount of fishing gear of a specific type used on the fishing grounds over a given unit of time; e.g., hours trawled per day, number of hooks set per day or number of hauls of a beach seine per day. When two or more kinds of gear are used, the respective efforts must be adjusted to some standard type before being added. El Niño: Abnormally warm ocean climate conditions which, in some years, affect the Eastern coast of Latin America (centered on Peru) often around Christmas time and which occasionally can be transmitted northward to Alaskan waters. The anomaly is accompanied by dramatic changes in species
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Dynamic Changes in Marine Ecosystems: Fishing, Food Webs, and Future Options abundance and distribution, higher local rainfall and flooding, and massive deaths of fish and their predators (including birds). Many other climatic anomalies around the world (e.g., droughts, floods, forest fires) are attributed to consequences of El Niño. elasmobranch: A group of fish without hard bony skeletons, including sharks, skates, and rays. eutrophication: Generally, the natural or man-made process by which a body of water becomes enriched in dissolved mineral nutrients (particularly phosphorus and nitrogen) that stimulate the growth of aquatic plants and enhances organic production of the water body. Excessive enrichment may result in the depletion of dissolved oxygen and eventually to species mortality. EwE (Ecopath with Ecosim models): Ecological/ecosystem software used to model the dynamics of the feeding interactions and nutrient flows in an exploited aquatic ecosystem. It is used to investigate the structural and functional attributes of each food web and to analyze the effects of alternative harvesting strategies on them. exploitation rate: The proportion of a population whose mortality was caused by fishing, usually expressed in an annual value. food web: The network of feeding relationships within an ecosystem or a community (i.e., the predator-prey relationships) that determines the flow of energy and materials from plants to herbivores, carnivores, and scavengers. genotype: The genetic make-up of an individual, different from its physical appearance (phenotype). growth overfishing: Fishing mortality in which the losses in weight from total mortality exceed the gain in weight due to growth. Growth overfishing results from catching too many small fish before they reached an optimum marketable size. harvest: The total number or poundage of fish caught and kept from an area over a period of time. hysteresis: The lag between making a change and the response to the change. impact analysis: A modeling system that identifies the impact of a change using costs and benefits. individual quota: The share of a total allowable catch (TAC) assigned to an individual, a vessel, or a company. If an individual quota is transferable, it is referred to as an Individual Transferable Quota (ITQ). individual transferable quota (ITQ): A type of individual quota allocated to individual fishermen or vessel owners and which can be bought and sold once distributed.
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Dynamic Changes in Marine Ecosystems: Fishing, Food Webs, and Future Options input control: Management instruments used to control the time and place as well as type and/or amount of fishing to limit yields and fishing mortality; e.g., restrictions on type and quantity of gear, effort, and capacity; closed seasons. interaction webs: A food web diagram depicting the strength of interactions among species; species are linked by arrows indicating the general consequences of altering the abundance or mass of critically important species. intertidal assemblage: A group of co-occurring populations, including both plant and animal species, living between the high and low water levels on marine shores iteroparous: A life history in which individuals reproduce more than once in a lifetime. keystone species: Individual species whose removal may engender dramatic changes in the structure and functioning of a biological community. logbook: A detailed, usually official record of a vessel’s fishing activity registered systematically on board the fishing vessel, usually including information on catch and its species composition, the corresponding fishing effort, and location. Completion of logbooks may be a compulsory requirement for a fishing license. marine protected area (MPA): Geographic area with discrete boundaries that has been designated to enhance the conservation of marine resources. This includes MPA-wide restrictions on some activities such as oil and gas mining and the use of zones such as fishery and ecological reserves to provide higher levels of protection. maximum sustainable yield (MSY): The largest average catch or yield that can continuously be taken from a stock under existing environmental conditions without significantly affecting the reproduction process. The MSY is also referred to as maximum equilibrium catch, maximum sustained yield, and sustainable catch. mean size: The average size of any particular group of fish. megafauna: Large or relatively large animals, as of a particular region or period, considered as a group. mortality: Measure of death rate. North Atlantic Oscillation (NAO): A complex climatic phenomenon in the North Atlantic Ocean especially associated with fluctuations of climate between Iceland and the Azores. It is characterized predominantly by cyclical fluctuations of air pressure and changes in storm tracks across the North Atlantic.
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Dynamic Changes in Marine Ecosystems: Fishing, Food Webs, and Future Options optimum yield: The harvest level for a species that achieves the greatest overall benefits, including economic, social, and biological considerations. Optimum yield is different from maximum sustainable yield in that the MSY considers only the biology of the species. The term includes both commercial and sport yields. output control: Management instruments aimed at directly limiting fish catch or landings through regulation of the total allowable catch and quotas. Pacific Decadal Oscillation (PDO): A decadal (20-30 year) pattern of Pacific climate variability. The PDO is detected as warm or cool surface waters in the Pacific Ocean, north of 20°N. During a “warm,” or “positive,” phase, the west Pacific becomes cool and part of the eastern Pacific ocean warms. paleoecology: The branch of ecology that deals with the interaction between ancient organisms and their environment. pelagic: Organisms that spend most of their life within the water column with little contact with or dependency on the bottom. May refer to only certain life stages of a species. perturbation: A physical or biological disturbance to a biological assemblage that can be rcognized by changes in species distributions or abundances. phenotype: The detectable outward manifestation of a specific genetic trait or genotype. piscivore: An organism that eats mainly fish. planktivore: An organism that consumes plankton. population: Organisms of the same species that occur in a particular place at a given time. A population may contain several discrete breeding groups or stocks. pristine: An environmental state in which anthropogenic influences are thought to be non-existent. purse seine: A fishing net with a line at the bottom that enables the net to be closed like a purse. Purse seines are very large and can be used to catch entire schools of fish. real-time data: Data which are reported almost simultaneously with collection. Real-time data are the most current information available, being collected and posted at essentially the same moment. recreational fisheries: The harvesting of fish for personal use, fun, and challenge (i.e., as opposed to harvest for profit or research). Recreational fishing does not include sale, barter, or trade of all or part of the catch. recruitment: A measure of the number of fish that enter a class during some time period, such as the spawning class or fishing-size class. regime shifts: A medium- or long-term shift in environmental conditions that impacts the productivity of a stock.
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Dynamic Changes in Marine Ecosystems: Fishing, Food Webs, and Future Options rehabilitation: To improve the quality of a habitat or ecosystem, but not necessarily to fully restore all functions to their undisturbed condition. restoration: To return an ecosystem to a close approximation of its condition prior to disturbance. The goal is to emulate a natural, functioning, self-regulating system that is integrated with the ecological landscape in which it occurs. sectoral management: Management approach in which specific agencies are given responsibility for managing particular sectors (e.g., fisheries, tourism, water quality), as opposed to integrated management in which various sectors are considered together. The result of sectoral management of an area in which different sectors compete for resources is often conflict between users, and between different sector management agencies with responsibilities over a common area, even under the same government. There is an inherent incentive for each sector to maximize its profits and benefits at the expense of other sectors, the general public, or the natural environment. sequential (or serial) addition: A term referring to the addition of new species to a fishery when stocks of the previous fishery species become depleted. The sequential addition of lower-trophic level species along with upper-trophic-level fisheries within an ecosystem is also known as “fishing through a food web.” sequential (or serial) depletion: A term referring to the systematic loss of species in a commercial fishery due to overfishing. The serial depletion of higher-trophic-level fisheries, and subsequent replacement with lower-trophic level species, is also known as “fishing down the food web.” Southern Oscillation: An oscillation in air pressure between the southeastern and southwestern Pacific waters. When the eastern Pacific waters increase in temperature (an El Niño event), atmospheric pressure rises in the western Pacific and drops in the east. This pressure drop is accompanied by a weakening of the easterly Trade Winds. Together with El Niño, this phenomenon is known as ENSO, or El Niño-Southern Oscillation. species density: The number of individuals per unit area or volume. stable state: A property of a community that, if the community is disturbed, it will tend to revert back to its original equilibrium state. It is possible for communities to have more than one stable state and different disturbances will drive community compositions to different alternative stable states. stock assessment: The process of collecting and analyzing biological and statistical information to determine the changes in the abundance of fishery stocks in response to fishing, and, to the extent possible, to predict future trends of stock abundance. Stock assessments are based on resource surveys; knowledge of the habitat requirements, life history, and behavior of the species; the use of environmental indices to determine impacts on stocks; and catch statistics. Stock assessments are used as a basis to assess and specify the present and probable future condition of a fishery.
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Dynamic Changes in Marine Ecosystems: Fishing, Food Webs, and Future Options sustainability: Characteristic of resources that are managed so that the natural capital stock is non-declining through time while production opportunities are maintained for the future. sustainable yield: The number or weight of fish in a stock that can be taken by fishing without reducing the stock biomass from year to year, assuming that environmental conditions remain the same. telemetry: The collection and transmission of data from remote locations to a central station. Thunnids: Tuna species. time-series: Measurements of data over time arranged in order of occurrence. Time series are often used to project future values by observing how the value of a variable has changed in the past. top-down management: A process of management in which information and decisions are centralized and in which resource users are kept outside of the decision-making process. total allowable catch (TAC): The annual recommended catch for a species or species group. The regional council sets the TAV from the range of allowable biological catch. total marine capture fisheries production: The total global harvest of marine capture fisheries (capture fisheries do not include production from aquaculture). trophic level: Position in food chain determined by the number of energy-transfer steps to that level. Plant producers constitute the lowest level, followed by herbivores and a series of carnivores at the higher levels. trophospecies: A group of species with similar trophic roles; i.e., species with similar foods and predators. utilized stock: The number of individuals within a stock that are alive at a given time but which will be caught in the future. year class: Individuals in a population that were born in the same year. For example, the 1987 year class of cod includes all cod born in 1987, which would be age 1 in 1988. Occasionally, a stock produces a very small or very large year class which can be pivotal in determining stock abundance in later years. yield: The production from a fishery, often given in weight. Catch and yield are often used interchangeably.
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