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Ice-breaker
A heavy weight joined to a length of rope by a few feet of chain, ice-breakers are commonly used by match anglers on frozen canals.

Ichthyology
The specific branch of zoology that deals with the study of fishes.

Imbricated
Lying lapped over each other in regular order (like scales of a fish or shingles on a roof).

Immigration
Referring to the movement of organisms into an area. See emigration and migrating.

Imprinting
The physiological and behavioral process by which migratory fish assimilate environmental cues to aid their return to their stream of origin as adults.

Inbreeding
Mating or crossing of individuals more closely related that average pairs in the population.

Incubation
The period of time from egg fertilization until hatching.

Indian reed
A buoyant material, also known as Sarkandas, often used to make wagglers.

Inferior mouth
The type of mouth that opens on the ventral surface (like sturgeon).

Inflated worm method Inserting an air bubble into a worm with a hypodermic needle

Instantaneous Rate Of Fishing Mortality
When fishing and natural mortality act concurrently, F is equal to the instantaneous total mortality rate, multiplied by the ratio of fishing deaths to all deaths. Also called; rate of fishing; instan- taneous rate of fishing; *force of fishing mortality .

Instantaneous Rate Of Growth
The natural logarithm of the ratio of final weigl1t to initial weight of a fish in a unit of time, usually a year. When applied collectively to all fish of a given age in a stock, the possibility of selective morta lity must be considered .

Instantaneous Rate Of Mortality
The natural logarithm (with sign changed) of the survival rate. The ratio of number of deaths per unit of time to population abundance during that time, if all deceased fish were to be immediately replaced so that population does not change. Also called; *coefficient of decrease.

Instantaneous Rate Of Natural Mortality
When natural and fishing mortality operate concurrently it is equal to the instantaneous total mortality rate, multi- plied by the ratio of natural deaths to all deaths. Also called; *force of natural mortality .

Instantaneous Rate Of Recruitment
"Number of fish that grow to catchable size per short interval of time, divided by the number of catchable fish already present at that time. Usually given on a yearly basis; that is, the figure just described is divided by the fraction of a year represented by the ""short interval"" in question. This concept is used principally when the size of the vulnerable stock is not changing or is changing only slowly, since among fishes recruitment is not usually associated with stock size in the direct way in which mortality and growth are."

Instantaneous Rate Of Surplus Production
"Equal to rate of growth plus rate of recruitment less rate of natural mortality--all in terms of weight and on an instantaneous basis. In a ""balanced"" or equilibrium fishery, this increment replaces what is removed by fishing, and rate of surplus production is numerically equal to rate of fishing. Also called; *instantaneous rate of natural increase."

Interorbital
The space between the eyes.

Introduction Ihe intentional or accidental placement of fish in a body of water; intentional scientific introduction of fish is also called "stocking"

In-line bomb
A bomb with a lengthways hole through which you run the line, mainly used in the larger sizes in rigs for carp.

Insert waggler
A waggler with a tip made from a short length of thin cane, reed, plastic or peacock quill, for greater sensitivity.

Invertebrate drift
Stream and terrestrial invertebrates that float with the current.

Inverted teardrop pole float
See 'body-up pole float'.

Irish brandling
A larger than normal type of brandling, found in Ireland.

Iteroparous
Species that reproduce repeatedly during their lifetime.