GLOSSARY

ALEVIN Life-history stage characteristic of catfishes and trouts that is equivalent to yolk-sac larva.

ALLOGENIC ECOSYSTEM ENGINEERS Organisms that alter the environment by transforming living or nonliving materials from one physical state to another and are not necessarily part of the modified physical structure.

ALLOPATRIC SPECIATION Formation of species through geographic isolation.

ALLOZYMES Variant forms of an enzyme that vary in their amino acid sequences and that are coded by different alleles at the same genetic locus.

AMMOCOETE The larval stage of lampreys.

AMPHIDROMOUS A type of diadromy in which the adult feeding and growing habitat and the spawning habitat are in the same biome (e.g., fresh water or sea). In freshwater amphidromy, movement from fresh water to the sea occurs during the larval stage, followed by a return migration to fresh water by early juveniles.

ANADROMOUS Type of diadromous life-history pattern characterized by movement from the sea to fresh water for purposes of spawning. After spawning, the young fishes move back to the sea where most of their feeding and growth occurs.

AREA CLADOGRAM Essentially taking a diagram of evolutionary relationships of taxa (i.e., cladogram) and replacing the taxa with their geographical areas; a way of reconstructing ancestral communities and determining causes of trait change.

AUTECOLOGY The study of how a single species interacts with its biotic and physical environments.

AUTOGENIC ECOSYSTEM ENGINEERS Organisms that transform their environment through endogenous processes, such as tree growth, and remain part of the altered environment.

BASIOCCIPITAL BONE The posterior-most bone of the neurocranium that contributes to the bottom and sides of the braincase and articulates with the first vertebra.

BET HEDGING Adaptations that minimize risk, such as reproducing over multiple years in a highly variable environment.

BUCCAL CAVITY Space enclosed by the cheeks and mouth and located anterior to the opercular chamber.

CATADROMOUS Type of diadromous life-history pattern characterized by movement from fresh water to the sea for purposes of spawning. After spawning, the young fishes move into fresh water, where most of their feeding and growth occurs.

CERATOBRANCHIAL bones Paired bones forming part of the ventral gill arches.

CHARACTER DISPLACEMENT Enhanced differences between two species where they occur together compared to locations where they occur apart.

CLADOGRAM A branching diagram showing the evolutionary relationships among taxa and based on cladistic methodology.

CONGENERIC Referring to species in the same genus.

COPEPODS Small crustaceans (class Copepoda), characterized by a cylindrical, segmented body; two terminal processes on the abdomen; and a head with a single eye and five pairs of jointed appendages.

CRATON A continental nucleus; a stable part of the continental lithosphere.

CRITICAL THERMAL MAXIMUM (CTM) A measure of tolerance to elevated water temperature in which water temperatures are steadily raised over a time period that is short enough to keep the fish from physiologically adapting yet long enough so that the core body temperature is equal to the water temperature. The endpoint is usually judged as the point at which the fish loses equilibrium.

CRUSTACEA Subphylum (sometimes considered a class) of primarily aquatic arthropods that includes crabs, shrimp, lobsters, crayfishes, cladocerans, and copepods.

CRYPSIS Traits reducing the risk of detection of an organism by a potential prey or predator when it is potentially perceivable to an observer.

COEFFICIENT OF VARIATION (CV) A relative measure of variation within a data set, calculated by dividing the standard deviation by the mean and usually multiplied by 100.

DARWINIAN DEBT Refers to the expectation that evolutionary recovery of a population from harmful genetic changes caused by various anthropogenic impacts takes longer than the amount of time required to cause the changes; it is a debt because the results of anthropogenic selection may result in evolutionary costs for future generations of the population.

DEME A local population united by interbreeding.

DEMERSAL Referring to organisms or objects that have negative buoyancy and occur on the bottom of water bodies.

DETRITUS Organic debris, such as accumulations of leaf particles, on a stream or lake bottom.

DIADROMOUS Life-history pattern characterized by periodic, physiologically mediated movement between the sea and fresh water; includes amphidromous, anadromous, and catadromous patterns.

DIATOMS Unicellular or colonial algae of the phylum Chrysophyta.

DYNAMIC LIFT Hydrodynamic lift; the lift generated by the movement of water over a hydrofoil.

ENDEMIC Occurring in a restricted area and nowhere else.

ENVELOPE OF DETECTION Distance away from a prey that a predator can locate it; its radius equals maximum visibility.

EPAXIAL Elements originating from above the axis of the notochord or vertebral column.

EPILIMNION In a thermally stratified water body, the warm, mixed layer of water located above the thermocline.

EPINEURAL Above the spinal cord; the dorsal surface of the vertebral centrum.

EPIPLEURAL Above the pleural ribs (the ribs above the body cavity).

ETHMOID BONES A series of small paired and median bones located anteriorly on the skull above the upper jaw.

EXAPTATION A character that enhances fitness but was not built by natural selection for its current role.

FITNESS The genetic contribution of an organism to subsequent generations.

FRY General term for a young fish at the age when the yolk sac has been absorbed and the fish is actively feeding. In salmonids the fry stage follows the alevin stage.

GENUS (PL. GENERA) Taxonomic category below the level of family that contains one or more species.

GEOGRAPHIC INFORMATION SYSTEMS (GIS) A system of computer programs that stores, edits, analyzes, and presents data that can be linked to a location, such as species locations, elevation, rainfall, soil types, water bodies, human population densities, and so on.

GNATHOSTOMES Referring to the Gnathostomata, the jawed vertebrates.

GONOCHORISTIC Having separate sexes.

HETEROTROPHY Obtaining nutrients by the consumption of organic matter.

HYDRAULIC RETENTION Measure of relative-complexity of a stream reach as determined by the time required for a dye to travel a specified distance through the reach.

HYOID APPARATUS Bony elements supporting the tongue and gill rakers and including the branchiostegal rays.

HYPAXIAL Elements originating from below the axis of the notochord or vertebral column.

HYPOLIMNION In a thermally stratified water body, the dense, cold layer of water located below the thermocline.

ICHTHYOLOGY Scientific study of fishes.

IMPOUNDMENT A body of water formed by damming a stream either by natural means (e.g., Beaver dams or landslides) or by human efforts (e.g., a reservoir).

INCLUSIVE FITNESS A measure of fitness that includes an individual’s own genetic fitness as well as its influence on the fitness of its kin.

INDUCIBLE DEFENSES Phenotypic responses by prey organisms induced by exposure to predators or to chemical cues from predators.

INFERIOR MOUTH The mouth is directed downward and the upper jaw and snout project beyond the lower jaw when the mouth is closed.

INSOLATION A measure of the amount of sunlight reaching the surface of an area.

INTRODUCED Used in reference to a nonnative species.

INVERTIVORES Predators of invertebrates.

IPSILATERAL On the same side of the body.

ITEROPARITY Breeding multiple times throughout the reproductive life span.

LACUSTRINE Referring to a lake or lake-like habitat.

LARVA (PL. LARVAE) The immature stage of fishes (or other taxa) prior to metamorphosis or transformation into the juvenile or adult form.

LEPTOKURTIC Frequency distribution in which there are more low values, fewer intermediate values, and more high values than would be predicted from a normal distribution.

MESOLARVA The second larval period characterized by the initial development of principal rays in the median fins.

METACENTRIC HEIGHT The difference between the center of mass and the center of buoyancy.

METALARVA The third larval period characterized by the formation of pelvic fin buds (when pelvic fins are present) and lasting until the fin-fold is completely resorbed.

MHC GENES Genes associated with the major histo-compatability complex (MHC) that are important in the immune system of vertebrates.

MYOSEPTA Sheets of connective tissue that separate blocks of axial muscles (myomeres) and onto which the muscle fibers insert.

NEUROCRANIUM The fairly rigid bony “box” surrounding the brain.

OOCYTE The developing egg cell in the female’s ovary that is formed from oogonia and is initially surrounded by follicular cells until ovulation.

OOGONIA Female reproductive cells that arise from primordial sex cells in or near the (peritoneal) germinal epithelium and are the precursor to oocytes.

PALATAL ORGAN An expansive patch of tissue on the roof of the pharynx containing numerous taste buds; in some suspension-feeding fishes it is papillate and covered in mucous.

PERIPHYTON A composite organic film found on aquatic substrata made up of algae, cyanobacteria, organic detritus, and other microbes.

PARR The third juvenile stage of salmonids, following the alevin and fry stages, that is characterized by species-specific patterns of vertical bars.

PHARYNGEAL JAWS Modified gill-arch elements, often bearing tooth pads, that are used in processing prey.

PHYSOSTOMES Fishes having a connection between the swimbladder and the mouth through a pneumatic duct.

POTAMODROMOUS Regular migration occurring wholly within fresh water.

PROSTAGLANDINS A group of unsaturated, polyoxygenated fatty acids; F prostaglandins are important in fish ovulation, the initiation of female sexual behavior, and also as a pheromone that attracts males to females.

PROTOCERCAL CAUDAL FIN A relatively undifferentiated caudal fin typical of lampreys and the larvae of most modern fishes.

ROTOLARVAE The initial larval period following hatching or parturition and which is characterized by the absence of distinct rays or spines in the median fins.

REALIZED NICHE The postinteractive niche, or the portion of the multidimensional niche that is actually occupied by a species, in contrast to the fundamental niche, which includes all areas of multidimensional space that a species might potentially occupy over all life stages.

REDD The gravel spawning depression excavated by salmonids.

SEMELPARITY Breeding only once in a lifetime.

SETIFORM TEETH Small, sometimes sharp, and usually very numerous teeth that are shaped like bristles or setae.

SMOLT The silvery, juvenile stage of anadromous salmonids that follows the freshwater-restricted parr stage and occurs prior to transitioning from fresh to salt water.

SPATULATE TEETH Rounded and flattened distally with a narrow shaft, much in the shape of a spatula.

STANDARD LENGTH (SL) Measured as the straight-line distance from the most anterior part of the snout to the base of the caudal fin (the hypural plate).

STATIC LIFT Buoyant lift, the lift produced by the inclusion in the body of low-density lipids or air bladders.

SUPERIOR MOUTH The mouth is directed upward and the lower jaw projects beyond the upper jaw when the mouth is closed.

SUSPENSORIUM A series of bones extending from the neurocranium, which forms the lateral wall of the mouth cavity and supports the jaw joint. It includes the quadrate, hyomandibula, pterygoids, symplectic, and preopercle bones.

SYMPATRIC Occurring within the normal range of one or more additional populations or species.

SYNECOLOGY The study of two or more species interacting in a community.

SYSTEMATICS The study of the evolutionary relationships among organisms.

TAXONOMY The branch of systematic biology concerned with the recognition, description, and hierarchical placement of taxa.

TERETE A streamlined body shape; cylindrical and tapering anteriorly and posteriorly.

TERMINAL MOUTH The mouth is directed forward with the upper and lower jaws approximately even.

THERMOCLINE In a thermally stratified body of water, the boundary between the upper (mixed) layer of warm water and the cold, dense (unmixed) layer of water.

TERRANE A discrete, fault-bounded crustal element that is added to a craton through plate movement.

VAGILITY Ability of an organism to move or disperse in an environment.

VISCOSITY Resistance of a fluid to deformation because of internal friction.

WEBERIAN APPARATUS Series of bony ossicles, formed from modified anterior vertebrae, that connect the swimbladder to the inner ear in the Otophysi (a large group including minnows, suckers, characins, and catfishes).

YOY Abbreviation of young-of-year in reference to fishes in their first calendar year of life (i.e., before January 1 of the year following hatching).