Comparison of vertical and horizontal swimming behaviour of the weather loach Misgurnus anguillicaudatus

Experiments on the swimming kinetics and behaviour of weather loach Misgurnus anguillicaudatus showed that horizontal swim speed was significantly greater than swim speeds when ascending to or descending from the water surface to gulp air. Vertical swimming speeds during ascending or descending were similar. Misgurnus anguillicaudatus swam unsteadily during vertical movements compared with horizontal movements.

Gender and gonadal maturity stage identification of captive Chinese sturgeon, Acipenser sinensis, using ultrasound imagery and sex steroids

Long lifespan and late maturation make it difficult to establish gamete maturity and breeding age of captive endangered Chinese sturgeon, Acipenser sinensis. This greatly handicaps timely breeding and future conservation stocking efforts. We used ultrasound imagery and sex steroids to determine the gender and gonadal maturity stage of captive Chinese sturgeon (age, 10-17years old). The echogenicity of the reproductive organs and the respective morphology of the gonads were described and two quantitative parameters p_o (proportion of the ovary to the entire reproductive organs) and d (thickness of the reproductive organs) were measured to characterize sex and maturity stage of Chinese sturgeon. Females were accordingly placed fish into several categories: F_II (F_II^-, F_II, F_II⁺), F_III (F_III, F_III⁺) and F_IV (F_IV, F_IV⁺) and F_VI and males as M_II, M_III, M_IV, M_V and M_VI. The accuracy of gender and maturity stage determination provided by ultrasonographic methods was 72.7% for F_II^- ovary (n=11) and 76.2% for M_II testis (n=42). Accuracy of sex and maturity determination using only serum sex steroid of testosterone (T) and estradiol-17β (E₂) was low (58-73%, depending on maturity stage). However, when the two methods were used together, accuracy increased sharply, especially for immature (II stage) females. In summary, of 151 Chinese sturgeon, whose sex and maturity stage were independently confirmed, 88.1% (n=133), 62.9% (n=95), and 96.7% (n=146) were successfully sexed and staged using ultrasound, sex steroids, or both methods, respectively. The results provide reliable non-invasive techniques for determining sex and gonadal maturation of captive Chinese sturgeon. These methods can track individual gonad characteristics over multi-year reproductive cycles, which will assist captive broodstock management, artificial reproduction, and future conservation stocking.

Migrations and movements of adult Chinese sturgeon Acipenser sinensis in the Yangtze River, China

From 2006 to 2009, 27 ultrasonic-tagged wild adult Chinese sturgeon Acipenser sinensis [eight males, 19 females; total length (L(T)) range = 245-368 cm] were captured on the spawning ground just downstream of Gezhouba Dam (GZD) in the Yangtze River. Twenty-six individuals were tracked for 7 to 707 days (mean number of relocations = 859; range = 3-4549). Acipenser sinensis movements were divided into four categories: (1) spawning migration, two tagged A. sinensis (one female and one male) returned to the Yangtze River and migrated from the Yangtze Estuary (river kilometer, rkm, 0) to the spawning ground (1678 rkm) between June and October. Their mean upstream ground speed was 1.41 km h(-1) (range = 0.26-2.35 km h(-1) ). The speed of the male was faster than the female; (2) pre-spawning holding, four of five females tagged in November 2008 stayed within 1678.00-1674.15 rkm for c. 1 year before the spawning period; (3) spawning movements, all A. sinensis swam mostly from the tailrace of the GZD (1678 rkm) to the Miaozui (1674.15 rkm) reach and some moved downstream c. 18.21 rkm (range = 3.93-24.64 rkm), but then, returned upstream to the GZD. Most tagged A. sinensis were on the spawning ground on the day when the spawning occurred; (4) post-spawning migration males (n = 6) and females (n = 2) departed the spawning area on a different time schedule, females leaving before males. The mean seaward ground speed of six A. sinensis was 4.87 km h(-1) (range = 0.68-7.60 km h(-1) ). There were no significant differences (P > 0.05) in ground speeds among reaches or between sexes within reaches between telemetry receivers. These broad spatiotemporal scale results will help establish an effective protection strategy for the species in the Yangtze River.

Experimental Study of Galvanonarcosis for Rainbow Trout (Salmo gairdneri) Immobilization

Galvanonarcosis treatments had no significant effect on growth or photonegative behavior of rainbow trout (Salmo gairdneri). The data indicate the potential usefulness of the technique for immobilizing fish.