First record of the Australian redclaw crayfish Cherax quadricarinatus (von Martens 1868) in Hong Kong, China

Invasive freshwater crayfish are spreading rapidly across the world. Here, we report the first record of Australian redclaw crayfish, Cherax quadricarinatus (von Martens 1868) in Hong Kong, China. Identification of the captured crayfish was confirmed using external morphological features and molecular analyses. A total of 49 crayfish were captured from a stream pool and a reservoir in Pok Fu Lam Country Park using dip nets and funnel traps. The captured C. quadricarinatus ranged from 17.20 mm to 56.40 mm (mean = 30.70) in carapace length and the sex ratio was 1:1. Since this species is globally recognized as an invasive species, a comprehensive survey on its status and invasion front, an investigation into its potential ecological impacts, as well as the formulation of a monitoring and removal strategy, are warranted.

Mallomonas cronbergiae (Chrysophyceae, Stramenopiles), A New Species from the Guineo-Congolian Rainforest in Cameroon

A new species of Mallomonas Perty, M. cronbergiae J. Piątek sp. nov., was found in a tropical shallow stream pool in the Guineo-Congolian rainforest in Cameroon. It belongs to the series Ouradiotae and is similar to the three other Mallomonas taxa from this series, namely M. ouradion Harris & Bradley, M. parvula Dürrschmidt and M. parvula var. nichollsii Wujek & Bland, but differs in some morphological characters that clearly differentiate M. cronbergiae as a distinct species. The new species has a different size of scales, characteristic 3–7 pores at the posterior rim, an anterior flange ornamented with papillae, and a shield thickly ornamented with papillae (14–16 per scale width). The species is described and illustrated with the use of light and scanning electron microscopy.

Effects of large woody debris placement on stream channels and benthic macroinvertebrates

Large woody debris (LWD) was added as an experimental stream restoration technique in two streams in southwest Virginia. Additions were designed to compare human judgement in log placements against a randomized design and an unmanipulated reach, and also to compare effectiveness in a low- and a high-gradient stream. Pool area increased 146% in the systematic placement and 32% in the random placement sections of the low-gradient stream, lending support to the notion that human judgement can be more effective than placing logs at random in low-gradient streams. Conversely, the high-gradient stream changed very little after LWD additions, suggesting that other hydraulic controls such as boulders and bedrock override LWD influences in high-gradient streams. Logs oriented as dams were responsible for all pools created by additions regardless of stream or method of placement. Multiple log combinations created only two pools, while the other seven pools were created by single LWD pieces. Total benthic macroinvertebrate abundance did not change as a result of LWD additions in either stream, but net abundances of Plecoptera, Coleoptera, Trichoptera, and Oligochaeta decreased, while Ephemeroptera increased significantly with the proportional increase in pool area in the low-gradient stream.

Structure and ecological production of the fish taxocene of a small floodplain system

Fish species richness in floodplain pools results from species addition by spring invasion from the stream and species subtraction by local extinction throughout the summer. Local extinction is the more important of the two components. Nineteen floodplain pools (1 to 597 m2) and an adjacent section of Irvine Creek (43°44′ N, 80°25′ W), Ontario, Canada, were treated with a piscicide to test if the pools contribute significantly to the resource potential of the river basin. Altogether, 41 626 fishes of 20 species were collected. Number of days of stream connection in the spring was not significantly correlated with fish species richness in the pools (P < 0.10). A significant correlation (P < 0.05, r = 0.7413) was found between species richness and the logarithm of pool area. The total fish production for the Irvine Creek section, adjusted to account for dominant and nondominant species, was 298 kg∙ha−∙year−1. Production for this site was underestimated by 49% when weights and densities were backcalculated to time of annulus formation. Total production estimates of the floodplain pools ranged from 135 to 314 kg∙ha−1∙year−1. Stream connection duration affects pool fish production by regulating accessibility to the young of stream spawning species. Floodplain pools are beneficial to the Irvine Creek system. As nursery areas, floodplain pools produce fish biomass which can return to the stream during periods of stream–pool connection. These pools may also act as fish havens if catastrophic stream mortality occurs.