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Juvenile coastal fish are drawn to turbid shallow waters and to mangrove structures, where they have better protection from predators. [ 11 ] [ 12 ] As the fish grow, their foraging ability increases and their vulnerability to predators decreases, and they tend to shift from mangroves to mudflats . [ 13 ]
Fish, eels, some lobsters, blue crabs (and so forth) do have distinct juvenile habitats, whether with or without overlap with adult habitats. In terms of management, use of the nursery role hypothesis may be limiting as it excludes some potentially important nursery sites. In these cases the Effective Juvenile Habitat concept may be more useful.
Juvenile fish have four to five bold vertical black bars on a light background and can be mistaken for sheepshead at first glance, but are distinguished on closer inspection because sheepshead have teeth and black drum have chin barbels. These stripes usually fade to dull gray as the fish grow from 12 to 24 inches (30 to 61 cm) in length.
Juvenile survival is dependent on very high quality water conditions. [7] [10] Feeding is an important component of the rearing process. Although many species are able to grow on maternal reserves alone (lecithotrophy), most commercially produced species require feeding to optimise survival, growth, yield and juvenile quality.
The species is known to grow to a maximum size of 51 cm and around 1.25 kg weight. [ 6 ] The fin anatomy is highly useful for identification purposes, with the species having 11 spines in the first dorsal fin , with one spine and 16 or 18 soft rays on the second dorsal fin.
These larvae are plankton-eaters and grow quickly. Between the ages of three and four weeks old, when they have reached a length of 15 to 20 mm (0.6 to 0.8 in), they descend to the floor as juveniles. Juvenile angelfish live alone and in territories encompassing finger sponges and coral, where they establish cleaning stations for other fish. [6]
Finally, juvenile sharks have been found to prefer the warmer water of shallow coastal areas as they grow into adulthood and swim in shark nurseries near the coast.
The demand for adult eels has continued to grow, as of 2003. Germany imported more than $50 million worth of eels in 2002. In Europe, 25 million kg are consumed each year, but in Japan alone, more than 100 million kg were consumed in 1996.