Length–weight relationships of two fish species from the Yangtze River,China

Fish samples for the study were collected from the Yangtze River in China. Length–weight relationships were determined for two endemic fish species (Leiocassis longirostris Günther, 1864 and Schistura fasciolata Nichols & Pope, 1927) for the first time.     

Measuring fish length and assessing behaviour in a high‐biodiversity reach of the Upper Yangtze River using an acoustic camera and echo sounder

In the past decade improved acoustic hard‐ and software have enabled estimations of abundance and distribution patterns of aquatic organism, including non‐intrusive monitoring of fish migrations and behaviour. In this study, a high frequency acoustic camera (DIDSON‐LR, 1.2 MHz, 0.7 MHz) and a portable split‐beam scientific echo sounder (Simrad EY60, 200 kHz) collected acoustic data on 192 and 157 individuals within 24 hr (19–20 April 2011) in the Mituo reach of the Yangtze River, China. Mean fish length estimated from the acoustic camera data was 18.7 ± 5.6 cm, with an average swimming speed of 0.19 ± 0.13 m s^?1. The mean fish target strength (TS) produced by the echo sounder was ?43.8 ± 4.4 dB, which corresponded to 5.7–119.9 cm fish length when converted by three different TS‐length equations. Average swimming speed was 0.11 ± 0.06 m s^?1 from the echo sounder. Compared with the actual fish catch by the three layers of drift gill net in the survey area, the target length indicated by DIDSON was more accurate than the EY60 results, which were highly affected by the choice of TS length equations. It was determined that the two devices used synchronously could estimate fish length effectively to investigate their behaviour and distribution.     

Effect of dietary L‐malic acid supplementation on growth,feed utilization and digestive function of juvenile GIFT tilapia Oreochromis niloticus (Linnaeus, 1758)

Two feeding trials (FTs) were conducted in 2013 and 2014, respectively, to determine the optimal L‐malic acid (LMA) level for juvenile GIFT (Genetically Improved Farmed Tilapia) Oreochromis niloticus. Except for the LMA level, the FT1 and FT2 had a similar diet formulation. In FT1, LMA was included at 0 (basal diet), 1, 4, 8, 16 and 32 g kg^?1, respectively. After 20 weeks, daily weight gain and feed conversion ratio were improved but not differentiated with 1–8 g kg^?1 LMA. Further increasing the LMA supply initially decreased the feed intake (16 g kg^?1), and then decreased both feed intake and feed utilization (32 g kg^?1), thus impairing the fish growth. FT2 was subsequently conducted with a smaller LMA range (0, 0.5, 1, 2, 4 and 8 g kg^?1, respectively) but was unfortunately terminated at the end of 8 weeks because 20% of the fish were badly injured during weighing. Unexpectedly, growth and feed utilization were still improved but not differentiated with 0.5–8 g kg^?1 LMA. In FT2, beneficial effects of LMA inclusion on the digestive function (pepsin, foregut amylase and foregut lipase), the activities of serum lysozyme and hepatic superoxide dismutase, and liver lipid peroxidation (malondialdehyde concentration) were found. Taking the results of FT1 and FT2 together, it could be concluded that dietary LMA supplementation at low concentrations (0.5–8 g kg^?1) could improve growth and feed utilization, but excess LMA (≥16 g kg^?1) might compromise feed intake and/or feed utilization, thus impairing fish growth. To reduce feed costs in commercial practice, 0.5 g kg^?1 LMA is recommended in the feed of juvenile GIFT tilapia based on the results of this study.     

Length–weight relationships for four fish species upstream in the Minjiang River,southeastern China

Length–weight relationships were determined for four fish species (Hemibarbus labeo Pallas, 1776; Tachysurus nitidus Sauvage & Dabry de Thiersant, 1874; Pseudobagrus vachelli Richardson, 1846; Glossogobius olivaceus Temminck & Schlegel, 1845) upstream in the Minjiang River in Fujian Province, southeastern China. Samples were collected employing various fishing gear in 2012–2013. The present report is the first record of the length–weight relationships for these species.     

Length–weight relationships for three fish species from the Yalong River,southwestern China

Length–weight relationships were determined for three fish species: Gymnodiptychus pachycheilus (Herzenstein, 1892), Discogobio yunnanensis (Regan, 1907), and Triplophysa pseudostenura (He, Zhang & Song, 2012). Samples were collected from the Yalong River, southwestern China using fishing gear (gillnets, 30 × 15 m, mesh‐size 5 mm) and electroshock fishing (CWB‐2000 P, 12 V, 250 HZ) in June 2007. Prior to this study, length–weight relationships for these three species were unknown. For two of the species [Discogobio yunnanensis (Regan, 1907) and Triplophysa pseudostenura (He, Zhang & Song, 2012)], new maximum standard lengths not yet reported in the scientific literature were noted.     

Plastic responses in the metabolome and functional traits of maize plants to temperature variations

Environmentally inducible phenotypic plasticity is a major player in plant responses to climate change. However, metabolic responses and their role in determining the phenotypic plasticity of plants that are subjected to temperature variations remain poorly understood. The metabolomic profiles and metabolite levels in the leaves of three maize inbred lines grown in different temperature conditions were examined with a nuclear magnetic resonance metabolomic technique. The relationship of functional traits to metabolome profiles and the metabolic mechanism underlying temperature variations were then explored. A comparative analysis showed that during heat and cold stress, maize plants shared common plastic responses in biomass accumulation, carbon, nitrogen, sugars, some amino acids and compatible solutes. We also found that the plastic response of maize plants to heat stress was different from that under cold stress, mainly involving biomass allocation, shikimate and its aromatic amino acid derivatives, and other non‐polar metabolites. The plastic responsiveness of functional traits of maize lines to temperature variations was low, while the metabolic responsiveness in plasticity was high, indicating that functional and metabolic plasticity may play different roles in maize plant adaptation to temperature variations. A linear regression analysis revealed that the maize lines could adapt to growth temperature variations through the interrelation of plastic responses in the metabolomes and functional traits, such as biomass allocation and the status of carbon and nitrogen. We provide valuable insight into the plastic response strategy of maize plants to temperature variations that will permit the optimisation of crop cultivation in an increasingly variable environment.