Pink salmon ( Oncorhynchus gorbuscha) is an anadromous salmonid originating in the North Pacific. Their impact on native biodiversity is associated with predation, competition, hybridization, energy transfer and transfer of parasites and diseases. Invasive alien species are among the most prominent threats to native biodiversity and ecosystems (Pejchar & Mooney, 2009 Rahel, 2002). Hence, late summer and early autumn was likely an important period for marine growth and survival in the invasive pink salmon. Scale growth during late summer and early autumn explained more of the variation in fish length at spawning (27%). If mortality is selective, removing fish with poor growth may reduce a correlation between early growth and body size at spawning. The reason for this may be large individual variation in growth combined with large mortality during the first weeks at sea. When dividing scale growth into three periods, better growth during the first period at sea was related to increased fish body length at spawning, but this early growth explained only a minor part (6%) of the variation in final body length. Fish body size at spawning was positively correlated with the distance from scale focus to the last winter circulus, as well as with the number of circuli. Growth declined to a minimum during winter. This was followed by a period of growth increase and stability during late summer and autumn, which may reflect a transition to better food sources, as the fish migrate from coastal waters to the open ocean, and as they grow larger and can eat larger and more energy efficient food items. Analysis of pink salmon scales from two rivers draining to the western Barents Sea showed declining growth during the first weeks after entering the sea, and some individuals even showed a pronounced growth arrest, based on detailed scale circulus analyses. 1960, but beginning in 2017 their numbers have exploded in rivers in northern Norway, with considerable numbers also recorded in rivers in southern Norway and other countries bordering the North Atlantic. It is possible to estimate how old a fish is by counting the bands, known as annuli.Invasive pink salmon ( Oncorhynchus gorbuscha) has been present in variable, but low, numbers in Norwegian waters since c. When the weather becomes cool, scale growth slows down and the circuli appear more closely together, leaving a dark band. Theses rings are similar to the growth rings in tree trunks.
The increase in size of the scales causes the development of growth rings known as circuli. As a fish with cycloid or ctenoid scales grows, its scales also grow. Interestingly, fish scales can be used to estimate the age of a fish. Both types of scales, however, consist of two main regions a rigid surface layer chiefly composed of calcium-based salts, and a deeper fibrous layer consisting mainly of collagen.
Conversely, cycloid scales have a smooth posterior edge as their name from the Greekcyclo, meaning circle, implies. The ctenoid variety have a comb-like, spiny posterior edge, their name developing from the Greek word cteno, meaning comb. There are four major groups, one of which is comprised of cycloid and ctenoid scales.
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