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Population density also matters in simpler environments because higher intraspecific competition causes a decrease in reproductive rate and somatic growth rate, and a corresponding increase in juvenile mortality rate due to cannibalism. [22] It was confirmed that in low-predation environments, guppy populations are in part regulated by density ...
Guppy fry. Livebearers are fish that retain their eggs inside the body and give birth to live, free-swimming young. They are especially prized by aquarium owners. Among aquarium fish, livebearers are nearly all members of the family Poeciliidae and include: guppies, mollies, platies and swordtails.
A fishery population is affected by three dynamic rate functions: Birth rate or recruitment. Recruitment means reaching a certain size or reproductive stage. With fisheries, recruitment usually refers to the age a fish can be caught and counted in nets. Growth rate. This measures the growth of individuals in size and length.
Bifurcation diagram of the Ricker model with carrying capacity of 1000. The Ricker model, named after Bill Ricker, is a classic discrete population model which gives the expected number N t+1 (or density) of individuals in generation t + 1 as a function of the number of individuals in the previous generation, [1]
Guppies are highly prolific livebearers [43] giving birth to between five and 30 fry, though under extreme circumstances, she may give birth to only one or two or over 100. The gestation period of a guppy is typically 21–30 days, but can vary considerably. The area where a pregnant guppy's abdomen meets the tail is sometimes called the ...
When they have developed to the point where they are capable of feeding by themselves, the fish are called fry. When, in addition, they have developed scales and working fins , the transition to a juvenile fish is complete and it is called a fingerling , so called as they are typically about the size of human fingers .
The algebraic symbols b, d and r stand for the rates of birth, death, and the rate of change per individual in the general population, the intrinsic rate of increase. This formula can be read as the rate of change in the population (dN/dt) is equal to births minus deaths (B − D). [2] [13] [17]
Yellow perch do not travel far during the year, but move into deeper water during winter and return to shallow water in spring to spawn. Spawning occurs in the spring when water temperatures are between 6.7 and 12.8 °C. Growth of fry is initiated at 6–10 °C, but is inactive below 5.3 °C.