The Fish Vet's Blog

When I was working in Tasmania, every year around spring time, fish farmers will be gearing up to move their fish from the freshwater ponds to the sea. How do you know when they’re ready? Visually, they will start to lose their parr marks, turning a wholly more silver colour.

When this happens, a random sample of fish are placed in seawater ponds for a ‘challenge’ trial. These fish are then taken to the lab and
we would take blood samples from salmon to check whether they were ready to go to sea. We would test their blood for any elevations in blood sodium or blood chloride. If they are able maintain these parameters within their normal reference range, then it means that the fish are ready to be trucked to sea cages. If not, then the fish are held back till they are ready.

But how does this affect the fish’s acid-base balance ? This paper tells us a little more…

Aquaculture
Volume 341, Number 5 (March 2012)
	The effect of environmental salinity on H+efflux in the euryhaline barramundi (Lates calcarifer)
	Authors:	J.C. Weakley, J.B. Claiborne, K.A. Hyndman, S.L. Edwards
	Author Affiliations:	no affiliations available
	Source:	Aquaculture, Volume 341, Number 5 (March 2012)
	Page Numbers:	190 – 196
	Available Full Text:	Full Text: Subscription Required to view full text Format: PDF Size: Unknown Location: Publisher’s Site Authentication: Publisher’s Site
	Abstract:	Euryhaline fishes such as the barramundi (Lates calcarifer), have the physiological ability to move between waters of various salinities and are often exposed to rapid changes in ionic gradients that may alter acid–base homeostasis. It has recently been proposed that these species may utilize gill H+ATPase and Na+/H+exchanger mechanisms to regulate systemic pH, and that the differential expression of the acid/base relevant transporters is governed by environmental salinity. This study examined acid–base regulation in juvenile barramundi adapted to fresh, brackish, or salt water (ranging from 0 to 32ppt) and exposed to 1% environmental hypercapnia. Our findings suggest that barramundi increase net acid excretion in all salinities tested, with a more rapid response observed in fish adapted 22,5 and 32ppt. In contrast, the relative change in net H+transfers was greatest in the groups adapted to the lower salinities. Fish in 15ppt exhibited an apparent relationship between increased in net H+excretion and increases in branchial H+ATPase protein expression.
	Citation:	J.C. Weakley, J.B. Claiborne, K.A. Hyndman, S.L. Edwards . The effect of environmental salinity on H+efflux in the euryhaline barramundi (Lates calcarifer). Aquaculture, Volume 341, Number 5 (March 2012), pp. 190-196, ;
	URL:	http://ejournals.ebsco.com/direct.asp?ArticleID=4209B784BA6F79B35F3F

Many fish breeders swear by feeding live or fresh foods to fish to condition them for breeding. This recently published scientific article finds evidence to support this long standing belief.

Aquaculture Research
Volume 43, Number 5 (April 2012)
	Examination of broodstock diet effects on egg production and egg quality in flame angelfish (Centropyge loriculus)
	Authors:	Chatham K Callan 1, Charles W Laidley 1, Ian P Forster1,2, Kenneth M Liu 1, Linda J Kling 3, Allen R Place 4
	Author Affiliations:	1: Finfish Program, The Oceanic Institute, Waimanalo, HI, USA 2: Center for Aquaculture and Environmental Research, Fisheries and Ocean Canada, West Vancouver, Canada 3: School of Marine Sciences, University of Maine, Orono, ME, USA 4: Columbus Center, Institute for Marine and Environmental Technology, University of Maryland Center of Environmental Science, Baltimore, MD, USA
	Source:	Aquaculture Research, Volume 43, Number 5 (April 2012)
	Page Numbers:	696 – 705
	Available Full Text:	Full Text: Subscription Required to view full text Format: PDF Size: unknown Location: Publisher’s Site Authentication: EBSCOhost EJS
	Abstract:	This study was conducted to determine the effects of broodstock diet on flame angelfish (Centropyge loriculus) reproduction and generate baseline spawning performance (mean fecundity, egg fertilization, egg viability) and egg biochemistry data for this species. Sixteen flame angelfish broodstock pairs were maintained on one of three formulated diets or a raw diet (consisting of squid, shrimp, fish eggs and algae) to determine the effect of diet composition on the fecundity, egg fertilization rates and egg viability over a 7-month period. Although all the diets supported similar mean spawn frequency and fecundity over the duration of the experiment, the mean fertilization rates and egg viability were significantly greater among pairs receiving the raw diet. Egg fatty acid composition was generally reflective of the maternal diet and similar to the values reported for other tropical species. In particular, dietary factors such as n-3 highly unsaturated fatty acid and ARA level (which were elevated in the raw diet and eggs from fish receiving that treatment) are correlated with egg quality and are therefore worthy of future investigation. Because of the ease of conditioning, adaptability to varied formulated diets and continuous, sustained reproductive output, flame angelfish are an excellent model for examining the factors affecting marine fish egg and larval quality.
	Citation:	Chatham K Callan, Charles W Laidley, Ian P Forster, Kenneth M Liu, Linda J Kling, Allen R Place . Examination of broodstock diet effects on egg production and egg quality in flame angelfish (Centropyge loriculus). Aquaculture Research, Volume 43, Number 5 (April 2012), pp. 696-705, <http://ejournals.ebsco.com/direct.asp?ArticleID=4EDBB8586FB70ADB920A&gt;
	URL:	http://ejournals.ebsco.com/direct.asp?ArticleID=4EDBB8586FB70ADB920A

Histopathological survey
of lesions and infections
affecting sick
ornamental fish in pet
shops in New South
Wales, Australia.
Wickins SC, et al. (2011).
Dis. Aquat. Organ., 94
(2):143-152.
Abstract
The objective of this
study was to describe the
frequency of the histopathological
lesions and categorize the evident infections
in sick ornamental fish from pet shops in New South
Wales, Australia. We examined 108 fish that had evidence
of morbidity or mortality, including 67 cyprinids,
25 osphronemids, 11 poeciliids, 4 characids and 1 cichlid,
sourced from 24 retail outlets.
Conditions frequently observed in the study population
included branchitis (62/86, 72.1%), visceral granulomas
(41/108, 38.0%), dermatitis (17/55, 30.9%),
wasting (31/108, 28.7%), and intestinal coccidiosis
(18/104, 17.4 %). Branchitis and dermatitis were usually
due to monogenean flukes, or flagellate or ciliate
protozoa. Intralesional Microsporidia (16/41, 39.0%),
Mycobacterium (7/41, 17.%), or Myxosporidia (5/41,
12.2%) were identified in the majority of fish with visceral
granulomas; however, special stains were critical
in their identification. The proportion of histologically
evident infections was remarkably high (77/108,
71.3%), and parasitic infections predominated.

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Check this one out, shared by my friend who’s into gadgets.

https://www.zazz.com.au/daily/thingy/5674