The Fish Vet's Blog

For help and advice with wild turtle issues ring:
0424 727 411 or 0424 727 624
www.turtleoblonganetwork.org.au/contact-us.html

Check out the Australian Veterinary Association’s (AVA) website, shared by Dr Jo Bannister:

http://www.ava.com.au/newsarticle/latest-fish-welfare-%E2%80%93-aaws-promotes-humane-despatch

Following the recent post on the potential for saprolegniasis affecting fish after a cold snap (mainly from depressed host immunity), many fish owners turn to malachite green as a potent antifungal cure. This chemical is still widely available in the ornamental fish sector.

But did you know that malachite green has long been banned for use in food fish production because of their carcinogenic potential. Actually, I met a guy who had inadvertently treated his silver perch with this chemical, only to find out some time later that it’s rather toxic and banned for use in food fish. So, he can’t eat his fish and instead, his cultured fish will now become lifelong pets.

This paper describes a different compound (peracetic acid) that may warrant further investigation and it could be something that can be used safely for fish that are destined for human consumption.

Journal of Fish Diseases
Volume 35, Number 7 (July 2012)
	Peracetic acid is effective for controlling fungus on channel catfish eggs
	Authors:	D L Straus 1, T Meinelt 2, B D Farmer 1, A J Mitchell 1
	Author Affiliations:	1: U.S. Department of Agriculture, Agricultural Research Service, Harry K. Dupree – Stuttgart National Aquaculture Research Center, Stuttgart, AR, USA 2: Department of Aquaculture and Ecophysiology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany
	Source:	Journal of Fish Diseases, Volume 35, Number 7 (July 2012)
	Page Numbers:	505 – 511
	Available Full Text:	Full Text: Subscription Required to view full text Format: PDF Size: unknown Location: Publisher’s Site Authentication: EBSCOhost EJS
	Abstract:	Peracetic acid (PAA) is a relatively new compound suggested for use to treat pathogens in aquaculture. It is approved for use in Europe, but not in the United States. This study determined the effectiveness of PAA for fungus control on channel catfish, Ictalurus punctatus(Rafinesque), eggs. The study consisted of five PAA concentrations (2.5, 5, 10, 15 and 20 mg L-1) and an untreated control in a flow-through system. A single spawn was used for each replication (N= 4). Eggs were treated twice daily until the embryos developed eyes. When hatching was complete for all viable eggs, fry were counted to determine the percent survival in each treatment. Fungal growth was severe in the untreated controls resulting in 11% survival. Treatments of 2.5, 5 and 10 mg L-1PAA were significantly different from the controls (P <;0.05). The highest percent survival of hatched fry was with 5 mg L-1PAA administered twice daily; the 2.5 mg L-1PAA treatment had slightly less survival, but gives a higher margin of safety in case of treatment error. Very little fungus was present in treatments receiving 2.5 mg L-1PAA or higher, and concentrations of 15 and 20 mg L-1PAA were toxic to the eggs. The mean survivals in the 0, 2.5, 5, 10, 15 and 20 mg L-1PAA treatments were 11%, 60%, 63%, 62%, 32% and 0%, respectively. Therefore, PAA may be a compound that merits further investigations regarding its use in U.S. aquaculture.
	Citation:	D L Straus, T Meinelt, B D Farmer, A J Mitchell . Peracetic acid is effective for controlling fungus on channel catfish eggs. Journal of Fish Diseases, Volume 35, Number 7 (July 2012), pp. 505-511, ;
	URL:	http://ejournals.ebsco.com/direct.asp?ArticleID=44C3AF30379B5B3A5154

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http://mobile.news.com.au/national/magic-dragon-in-an-azure-aussie-ocean/story-fndo4bst-1226511772994

What coincidence! I consulted with a client today about nitrite toxicity that occurred 2 weeks after he’d cleaned his filter a little too thoroughly using tap water!

Also, one of the co-authors, Dr Emily Donaldson is a colleague I met during Aquavet II last June!

Journal of Fish Diseases
Volume 35, Number 12 (December 2012)
	Effect of chloride on nitrite-induced methaemoglobinemia in Atlantic sturgeon, Acipenser oxyrinchus oxyrinchus(Mitchill)
	Authors:	M A Matsche, E Markin, E Donaldson, A Hengst, A Lazur
	Author Affiliations:	no affiliations available
	Source:	Journal of Fish Diseases, Volume 35, Number 12 (December 2012)
	Page Numbers:	873 – 885
	Available Full Text:	Full Text: Subscription Required to view full text Format: PDF Size: unknown Location: Publisher’s Site Authentication: EBSCOhost EJS
	Abstract:	We evaluated the effects of chloride concentration on the clinical pathology in juvenile Atlantic sturgeon, Acipenser oxyrinchus oxyrinchus(Mitchill),following semi-static exposures to 1 mg L-1nitrite for 96 h. In spring water naturally low in chloride (5 mg L-1), plasma nitrite concentrated to more than 40× environmental levels resulting in a severe methaemoglobinemia characterized by torpid behaviour, 30-fold increase in methaemoglobin fraction, anaemia, leucopenia and hyperkalaemia. Loss of intracellular water and potassium to extracellular space may have resulted in hyperkalaemia and haemodilution. Fish survived nitrite exposure, but 60% of torpid fish died following capture and tissue sampling. Fish acclimated to 10-fold higher chloride content (55 mg L-1) did not concentrate nitrite in the plasma above environmental levels or develop methaemoglobinemia, but did exhibit similar haematology and plasma chemistry changes. Plasma nitrite returned to preexposure levels by 14 days following nitrite exposures, but severity of clinical pathology changes persisted or increased, suggesting that Atlantic sturgeon have reduced capacity to recover from methaemoglobinemia. Fish that survive methaemoglobinemia may be susceptible to mortality from the cumulative effects of intoxication, handling and other stresses for two or more weeks following nitrite remediation. Chloride buffering in aquaculture systems reduces the toxic effects of nitrite accumulation.
	Citation:	M A Matsche, E Markin, E Donaldson, A Hengst, A Lazur . Effect of chloride on nitrite-induced methaemoglobinemia in Atlantic sturgeon, Acipenser oxyrinchus oxyrinchus(Mitchill). Journal of Fish Diseases, Volume 35, Number 12 (December 2012), pp. 873-885, <http://ejournals.ebsco.com/direct.asp?ArticleID=486DAA50900EBDFBB1BD&gt;
	URL:	http://ejournals.ebsco.com/direct.asp?ArticleID=486DAA50900EBDFBB1BD

Please find on my Facebook “Fin” page, some products that I find useful and have made available for purchase –

If the product you’re after is not already here, please send an email enquiry to: thefishvet@gmail.com

Thinking of breeding fish and growing them out? This paper describes that feeding regimes most conducive to growth do not necessarily maximize reproductive success in the zebra danio. Feeding frequency for reproductive success is once every couple of days to to 3x/day, whereas to maximise growth rate, feeding them 5x/day is optimal.

Aquaculture
Volume 369, Number 1-2 (November 2012)
	The effects of feeding frequency on growth and reproduction in zebrafish (Danio rerio)
	Authors:	Christian Lawrence, Jason Best, Althea James, Kara Maloney
	Author Affiliations:	no affiliations available
	Source:	Aquaculture, Volume 369, Number 1-2 (November 2012)
	Page Numbers:	103 – 108
	Available Full Text:	Full Text: Subscription Required to view full text Format: PDF Size: Unknown Location: Publisher’s Site Authentication: Publisher’s Site
	Abstract:	In the present study, we examined the effects of feeding regime on growth and reproductive performance in wild-type zebrafish (Danio rerio) maintained on a recirculating aquaculture system. Starting at 30days post-fertilization (dpf), we fed 8 replicate groups of age and strain matched fish a pelleted formulated diet (Gemma Micro 300, Skretting) either once every other day (EOD), one time (1×), three times (3×) or five times (5×) a day to achieve a total daily feed input of 5% of body weight per day compared against a “standard” control (C) of Artemia salinanauplii/metanauplii three times daily to apparent satiation. Fish in each treatment group were weighed and measured for fork length once every other week until 150dpf. We evaluated the effects of these feeding regimes on reproductive performance (breeding success, fecundity, and embryo viability) by setting up randomly sampled fish from each replicate groups in small group crosses (2 males, 3 females) once every other week starting at 76dpf until the experiment was terminated at 191dpf. Growth performance was significantly affected by feeding regime, especially in female fish, where fish in the 1×, 3×, and 5× groups were significantly (p<0.05, one way ANOVA) longer and heavier than fish in control and EOD groups at the end of experiment. Feeding regime had a less clear effect on reproductive performance. Mean fecundity and embryo viability varied little between groups, but the fish fed EOD, 1× and 3× showed significantly higher rates (p<0.05) of breeding success than the control and 5× groups. These results suggest that feeding regimes most conducive to growth do not necessarily maximize reproductive success in this species.
	Citation:	Christian Lawrence, Jason Best, Althea James, Kara Maloney . The effects of feeding frequency on growth and reproduction in zebrafish (Danio rerio). Aquaculture, Volume 369, Numbers 1-2 (November 2012), pp. 103-108, <http://ejournals.ebsco.com/direct.asp?ArticleID=429B9A2DF011828948DD&gt;
	URL:	http://ejournals.ebsco.com/direct.asp?ArticleID=429B9A2DF011828948DD

For a fish foot spa in Cambodia!

Those growing out barramundi in their Aquaponics setup will most likely experience issues with the cool weather, and the most common is saprolegniaisis. Make sure you run your UV and enrich their diet with vitamin C. Feed sparingly during the cool weather. If possible to heat their tanks, the better it is. Keep water temperature above at least 20-22 degrees Celsius.

Similar conditions can happen with cool water tolerant fishes such as koi and goldfish. So, keep an eye on them.

A toxic algae contaminates the filter-feeding shellfish. The toxin is not inactivated by cooking or freezing. My veterinary epidemiologist colleague suggests that maybe it’s an indication of rising sea temperatures allowing this algae to grow in locations where conditions were previously unsuitable.

Read more…
http://aquatichealth.net/node/63795