CHAPTER 10
GROWTH, MATURITY AND MORTALITY
The growth rates of euphausiids, how long they take to mature
sexually, when they breed, their fecundity and life expectancy are all
topics that have received considerable attention in recent years. Most
of this information has been procured through statistical analyses of
natural populations even although there are inherent difficulties in
doing this. Many euphausiids live in the open sea and if a sample is
taken a t a specified position and the ship returns there a few days or
weeks later there is no guarantee that the same population of euphausiids will still be there because the original population may have moved
away with shifting water masses. If, however, the same population
can be continuously sampled over a lengthy period of time then the
individuals in the samples can be measured and the changing numbers
of animals within each range of a series of ranges of measurements can
be plotted as length/frequency histograms (Fig. 113). A considerable
TABLE XXmII. ANALYTICAL STUDIES O F POPULATIONS OF EUPHAUSIIDS
Species
Sea area
Authorities
Thysanopoda acutifrons
Meganyctiphanes norvegica
Euphausia superba
Euphausia paci$ca
Euphausia triacantha
Thysanoessa raschii
Thysanoessa inermis
Thyanoessa longipes
Thysanoessa spinifera
Thysanoessa longicaudata
N. Atlantic
Einarsson (1945)
N. Atlantic
Wiborg (1966)
Mediterranean Ruud (1936)
Antarctic
Ruud (1932), Fraser (1936),
Einarsson (1945), Mauchline (1960),
Bargmann (1945), Nemoto (1959),
Marr (1962)
N. Pacific
Nemoto (1957)
Antarctic
Baker (1959)
N. Atlantic
N. Atlantic
N. Pacific
Nemoto (1957)
N. Pacific
Nemoto (1957)
N. Pacific
Nemoto (1957)
N. Atlantic
Einarsson (1945)
Dunbar (1940), Einarsson (1945),
Dunbar (1940), Einarsson (1945),
Mauchline (1966a)
Wiborg (1966)
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