bry’s sturgeon is adaptable to a variety of habitats,
individuals prefer sublittoral areas 10-20 m from
the river bank, with current velocity of about 1 m s-1,
water depth of 8-10 m, sandy silt ground and an
abundance of detritus and benthic organisms dur-
ing most of the year.
ty is calculated by the following equation: F = DW/
BW × 10000, where F is the feeding intensity, DW is
the diet weight in stomach, and BW the total body
weight. Feeding intensity varies indirectly with
standard body length according to the following re-
lationship: F=3337L-1.0213.Feeding habits Age and growth
Feeding habits of Dabry’s sturgeon vary with age, Wc usually age specimens of Dabry's sturgeon by
season and habitat. Their food items arc wide-rang- grinding sections of either a dorsal scute or an oper-
ing. Although Dabry’s sturgeon prefer living an- culum and counting the annuli. Table 3 shows the
mal prey, seeds, leaves and stems of plant remains results of a study of individuals from upper reaches
arc frequently found in analyses of stomach con- of the Yangtze River. In this sample. 92% of the in-
tents. Dietary variation during different life stages dividuals were younger than 3 years (Fu 1988). This
is shown in Table 2. Young fish initially feed almost is consistent with other studies that suggest that Da-
exclusively on zooplankton and oligochaetes. Ol- bry's sturgeon achieves maturity faster than other
der individuals eat oligochaetes and small fishes, sturgeons. Three year old fish can reach 3 kg in
such as gobies, as well as many other food items, weight. Between 3-4 years and 7-S years. growth
including chironomids, odonates, and aquatic rates in wild populations usually decline at sexual
plants (Zen et al. 1990). Tu (1980) reported that a 12 maturation. Males reach sexual maturity at 4- 6
cm Dabry’s sturgeon ate gobies up to 2 cm in length. years of age and females at 6-8 years of age. In pond
From May to July, the diet is broadest. Dabry’s stur- culture, Dabry's sturgeon can grow very rapidly (up
geon feeds throughout the winter. Typically, feed- to 3. 5 kg each year. L. Ling personal communica-
ing is more active at night than during the day. tion). Females generally grow slightly faster in
Feeding habits of Dabry’s sturgeon are influence- length than males. and at maturity, they usually
ced by environmental factors, such as water level weigh more than do males of the same length or age
fluctuations. Because benthic food organisms are because of their large ovaries.
concentrated in sublittoral areas. these arc the pre- The relationship between age (a) and length (L)
ferred feeding grounds. Cor the ages contained in the data set is L = 36 + 9.9a.
Tu (1980) studied the feeding intensity (F) of Da- This relationship does not follow the von Bertalanf-
bry’s sturgeon as a function of size. Feeding intensi- fy growth model. The relationships between bodyTable 3. Growth of wild Dabry’s sturgeon in upper reaches of Yangtze River (modified from Zen et al. 1090 and Fu 1988).
Age Weight (kg) Length (cm) NMean Annual increase Mean Annual increase0 0.08 21.3 66
1 0.65 0.55 44.1 22.8 24
2 1.30 0.68 55.0 10.9 8
3 3.05 1.75 68.2 13.2 6
4 4.25 1.20 77.5 9.3 4
5 6.60 2.35 86.5 9.3 4
6 8.60 2.00 95.5 9.0 3
7 11.85 3.25 101.0 5.0 3
8 14.70 2.85 106.0 5.0 2