River regulation alters the thermal regime of many freshwater ecosystems, and impoundments are known to negatively impact the recruitment of fluvial Burbot Lota lota populations. Some conservation programs in North America and Eurasia have begun to incorporate stocking of hatchery Burbot to mitigate extirpation risks. Anthropogenic modification of river temperatures and population structure has unknown implications for Burbot reproduction. This study evaluated the effects of elevated water temperatures and different maternal ages on spawning and embryo development of hatchery Burbot. Juveniles stocked downstream of a hydroelectric dam were found to naturally mature in a warmer postdam regime. The river‐adapted hatchery adults volitionally spawned in a broodstock facility at 2, 4, and 6°C. The spawning period spanned 18 d at 2°C but was shortened to 6−7 d at 4°C and 6°C. Survival of embryos to the eyed stage was 86.7, 47.9, and 0.1% at incubation temperatures of 2, 4, and 6°C, respectively. Embryo deformity increased dramatically between 4°C and 6°C. Young (age‐3) and old (age‐7 and older) females spawned 4−12 d later than 5‐ and 6‐year‐old females. Age‐3 females spawned smaller eggs, but no relationship was found between maternal age and embryo vital rates. It was concluded that juvenile stocking supplemented the abundance of reproductive adults in the highly altered ecosystem of the lower Kootenai River. Spawning temperatures above 4°C potentially underlie Burbot recruitment bottlenecks in systems affected by impoundments, climate warming, or other barriers to coldwater spawning habitat. Contraction of the spawning period by warmer temperatures, a truncated population age structure, or both could synchronize spawning to coincide with suboptimal conditions for normal embryo development.

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Abstract— —The occurrence of cataract in fresh‐water fish has recently been the cause for increasing concern amongst anglers who have been catching a steadily falling number of fish in several regions. It has been known for over 100 years that certain fish may become infested with a trematode (or fluke) which has a remarkable predilection for the lens. The life cycle begins in the intestine of the seagull where the adult trematode produces ova which are excreted on to the waters of reservoirs and lakes. The ova hatch out into miracidia which in turn invade water snails to form a sporocystic stage. Cercariae emerge from the snail and swim free to burrow into the body of a fish and find their way to the crystalline lens. The cycle is completed by the consumption of the fish by the gull in which the adult trematode once more develops. The purpose of this communication is to demonstrate the histological changes produced in the lens by the trematode. Résumé— —L'augmentation de l'incidence de la cataracte du Poisson d'eau douce a été récemment la cause de l'inquiétude croissante des pécheurs qui prennent une quantité sans cesse diminuée de Poisson dam différentes régions. Il est connu depuis plus de cent ans que certains poissons peuvent être infectés par les trématodes (ou douves) qui se logent avec une nette prédilection dans le cristallin. Le biocycle débute dam l'intestin de la mouette ou le trématode adulte pond des oeufs qui sont excrétés dans les eau des réservoirs et des lacs. Les oeufs donnent naissance am miracidies qui à leur tour envahissent les escargots d'eau et s'y transforment en sporocystes. La cercaire se libère de l'escargot et nage librement pour se loger dans le corps d'un Poisson et se frayer un chemim jusqu'au cristallin. Le cycle est achevé par l'ingestion du Poisson par la mouette chez laquelle le trématode adulte continue à se développer. Le but de cet article est de décrire les lésions histologiques du cristallin produites par le trématode. Zusammenfassung— —Das Auftreten von Katarakten bei Süsswasserfischen gab vor kurzem Anlass für steigende Besorgnis unter Anglern, die in mehreren Gebieten nur eine ständig abnehmende Zahl von Fischen fingen. Es ist seit über 100 Jahren bekannt, dass bestimmte Fische von Trematoden (Saugwürmer) befallen werden können, die eine merkliche Bevorzugung der Augenlinse zeigen. Der Lebenszyklus beginnt im Darm der Seemöwe, wo die envachsenen Trematoden Eier legen, die auf Wasserflächen von Staubecken und Seen ausgeschieden werden. Aus den Eiern gehen Mirazidien hervor, die ihrerseits Wasserschnecken befallen und dort ein sporozystisches Stadium bilden. Aus den Schnecken gehen dann Zerkarien hervor, die frei umherschwimmen und nach dem Eindringen in den Körper eines Fisches den Weg in die Augenlinse finden. Der Zyklus wird dadurch gesch‐lossen, dass die Möwe den Fisch frisst und dass sich in dem Vogel abermals die erwachsenen Trematoden entwickeln. Der Zweck dieser Mitteilung besteht in der Beschreibung der histologischen Veranderungen, die von den Trematoden in de...

Regional stakeholders in various nations are investigating the restoration of imperiled and extirpated Burbot Lota lota populations via the stocking of hatchery‐produced fish. Although stocking programs routinely tag fish for monitoring and evaluation projects, there is currently only limited information available regarding effective tagging techniques for use with juvenile Burbot. We identified two anatomical locations (dorsal muscle and peritoneum) that were suitable for PIT tag implantation and six body sites (snout, periocular region, nape, pectoral fin base, dorsal fin base, and ventral [anal fin base]) that were suitable for coded wire tag batch marking of age‐0 Burbot (88–144 mm TL). Our evaluation of these implantation methods generally revealed a high rate of tag retention (>95%) and no significant tagging effects on fish survival or growth. A follow‐up study also demonstrated satisfactory mass‐marking rates for both tag types. Coded wire tags and PIT tags should provide harmless, affordable, long‐term identification of hatchery Burbot juveniles. Received August 27, 2013; accepted December 27, 2013

A conservation program developed by regional stakeholders incorporates stock enhancement as one of several approaches to restore an imperiled Burbot Lota lota population native to Idaho and British Columbia. Tagging juvenile fish is pivotal to stock enhancement monitoring; however, limited information is currently available on marks or tags applied to Burbot. We identified six criteria to guide artificial marker selection that are specific to imperiled juvenile fish. A short-term experiment with age-0 Burbot (65-92 mm TL) tested fin clips, freeze brands, visible implant elastomer, passive integrated transponders, and an unmarked control group. At 4 weeks posttagging, no significant differences were found between marking treatments with respect to fish survival (100%), absolute growth rate (0.15 ± 0.06 mm/d), specific growth rate (0.55 ± 0.32 g·g −1 ·d −1 ), or condition factor (0.64 ± 0.05). Mean tag retention ranged from 88% to 100%, and no significant differences were detected between treatments. Recognition of dorsal freeze brands differed significantly between two independent tag assessments. Overall, we found no adverse short-term effects and high tag retention in this preliminary trial of seven artificial marks applied to hatchery-reared Burbot.

Summary The goal of this study was to evaluate four implantation techniques by assessing transmitter retention, survival, growth, and wound healing responses in white sturgeon (Acipenser transmontanus Richardson, 1836). A new acoustic transmitter (AT; cylindrical, 0.7 g in air, 24.2 × 5.0 mm, up to 365 days battery life) was developed to monitor age‐0 sturgeon; however, an implantation technique is critical to provide guidance for its use in field research. Sturgeon (n = 150, 182–289 mm fork length, 35–116 g) were separated into five treatments (n = 30 per treatment): (i) control, (ii) flank incision with one suture, (iii) flank incision without a suture, (iv) offline incision with one suture, and (v) offline incision without a suture. Fish were implanted with a non‐functioning AT and observed for 28 days. Transmitter retention was 100% and only fish in the offline incision without a suture treatment had reduced growth (0.15% mm growth per day) compared to controls (0.38%) over the 28 days study. Suturing caused an increase in incision inflammation, ulceration, and water mold infection. Offline incisions were more susceptible to varicosities than flank incisions. Non‐sutured incisions showed greater incision openness, but only during the first 14 days post‐implantation. A flank incision without a suture is recommended for implanting this new AT in age‐0 white sturgeon.

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