Acute Toxicity of Salt Cavern Brine on Early Life Stages of Striped Bass (Morone saxatilis).

A plan to create solution-mined salt caverns for natural gas storage by discharging brine into the Shubenacadie River estuary poses a potential risk to an "endangered" stock of striped bass. Toxicity of brine made from both salt-core and artificial sea-salt "Instant Ocean" was assessed by 1-h acute toxicity tests at both 19 °C and 12 °C, the typical thermal range in June, post-spawning. The short test duration was justified given the rapid dilution of the brine in the macrotidal estuary. The median lethal concentration (LC50 1 h) 95% confidence intervals of salt-core brine at 19 °C for eggs was 51-60 parts per thousand (ppt); yolk-sac larvae 34-55 ppt; first-feeding stage larvae (6-8 mm total length, TL) 37-44 ppt, and 30-46 ppt for large larvae (14-20 mm TL). Among juveniles, the median lethal concentration was significantly higher compared to larvae: 51-58 ppt for early juveniles (4-cm fork length, FL) and 63-67 ppt for juveniles 12-cm FL. The toxicity of brine made from either Instant Ocean or salt-core was similar. At 12 °C, yolk-sac larvae salinity tolerance was 30% lower than at 19 °C, whereas other life stages exhibited a similar response to 12 °C and 19 °C. The threshold observed effect concentration (TOEC) of the salt-core ranged from 24.4 ppt on large larvae to 59.7 ppt on 12-cm juveniles. In conclusion, a very low direct threat to striped bass is estimated for the discharge of brine into the Shubenacadie River estuary.

Saprolegnia molecular phylogeny among farmed teleosts in Nova Scotia, Canada.

To identify the pathogens causing saprolegniosis among farmed fish in Nova Scotia, 172 infected tissues and 23 water samples were collected from six species of teleosts: Atlantic salmon (Salmo salar), brown trout (Salmo trutta), Arctic charr (Salvelinus alpinus), brook trout (Salvelinus fontinalis), striped bass (Morone saxatilis) and rainbow trout (Oncorhynchus mykiss) at nine facilities over a 600 km range. Following laboratory culture, 132 isolates were recovered. Six species of oomycetes were identified from analysis of the internal transcribed spacer (ITS) sequence of the nrDNA: Saprolegnia parasitica, Saprolegnia ferax, Saprolegnia diclina, Saprolegnia aenigmatica, Saprolegnia torulosa, Saprolegnia sp. and Pythiopsis cymosa. Further phylogenetic analyses of the ITS and cytochrome c oxidase subunit 1 (Cox1) regions revealed four strains of Saprolegnia parasitica (named here as S1, S2, S3 and S4), of which S1 and S2 were common (37% and 42% of the isolates), and two strains of S. ferax. Among S. parasitica, S2 and S3 are more closely related to each other than to S1 based on the phylogenetic analyses and predicted RNA secondary structure of the ITS region. Sexual structures with a similar morphology were formed by S1 and S3 in vitro, but were not formed by S2.

Light intensity and suppression of nocturnal plasma melatonin in Arctic charr (Salvelinus alpinus).

The problem of early sexual maturation among farmed Arctic charr and other salmonids can be effectively reduced by 24 h light overwinter, provided it is bright enough to over-ride interference from the natural daylength cycle. To determine the threshold light intensity to suppress the nocturnal elevation of plasma melatonin, three groups of individually tagged fish (n = 26-28/group ca. 1040 g) were reared on 12 h light: 12 h dark (LD 12:12) and subjected to nighttime light intensities of either 50-65, 0.1-0.3 or 0 (control) lux for five months (November to April). Daytime light intensity was 720-750 lx. Diel plasma melatonin profiles in both November and April were similar; mean daytime levels ranged from 20 to 100 pg/ml, and nighttime levels were inversely proportional to light intensity. In the control group at 0 lx, plasma melatonin increased about four-fold after lights-off, ranging between 320 and 430 pg/ml. Nighttime light intensity of 0.1-0.3 lx halved plasma melatonin levels to 140-220 pg/ml, and 50-65 lx further reduced the levels to one quarter of the control group, 68-108 pg/ml. Among the lit groups, daytime plasma melatonin levels were about 20-30 pg/ml, significantly lower than the nocturnal levels suggesting the diel hormonal rhythm was not completely abolished. Fish grew steadily from about 1100 g to 1600 g between November and April, independent of light intensity (P = .67). Overall, the study demonstrated the sensitivity of pineal melatonin hormone to different light intensities in Arctic charr.