Mass marking coho salmon, 

 Oncorhynchus kisutch, fry 

 with lanthanum and cerium 



Bridget C. Ennevor 



Department of Fisheries and Oceans. 327-555 West Hastings Street 

 Vancouver. British Columbia, Canada V6B 5G3 



Most current salmonid tagging 

 programs identify small propor- 

 tions of a population. However, 

 under some circumstances it is 

 desirable to mark entire popula- 

 tions. Chemical marking is a tech- 

 nique that can rapidly mark large 

 numbers offish without individual 

 handling. Marking is accom- 

 plished by exposing the fish to bio- 

 logically rare elements that are 

 subsequently incorporated and 

 retained in certain tissues in 

 which they are not naturally 

 found. Marking of entire hatchery 

 populations could be valuable from 

 a fisheries management perspec- 

 tive for stock identification (hatch- 

 ery versus wild salmon), assess- 

 ment of contribution to fisheries, 

 and evaluation of current tagging 

 and sampling techniques. 



Ennevor and Beames (1993) 

 have shown that some lanthanide 

 elements (i.e. lanthanum and ce- 

 rium) are suitable for mass mark- 

 ing juvenile coho salmon, 

 Oncorhynchus kisutch. The lan- 

 thanide elements are not absorbed 

 from the gastro-intestinal tract 

 (Kyker, 1961; Ellis, 1968; Luckey 

 and Venugopal, 1977), and there- 

 fore may be introduced through 

 the fishes' rearing water. Because 

 these are bone-seeking elements 

 (Durbin et al., 1956; Jowsey et al., 

 1958), administered lanthanides 

 are subsequently incorporated into 

 the bony tissues of coho salmon fry 

 and smolts (Ennevor, 1991; 

 Ennevor and Beames, 1993). 



Analysis of the vertebral column, 

 otoliths, and scales by inductively 

 coupled plasma-mass spectrom- 

 etry (ICP-MS) revealed that ad- 

 ministered lanthanides are 

 present in these bony tissues 10.5 

 months post-treatment (Ennevor, 

 1991; Ennevor and Beames, 1993). 

 ICP-MS is capable of detection and 

 quantification of the lanthanide 

 elements at levels as low as 

 0.01 Ug-g -1 (Longerich et al., 1987; 

 Houk and Thompson, 1988). 



Trials were performed to deter- 

 mine whether immersion into so- 

 lutions of lanthanide elements 

 would produce recognizable marks 

 on juvenile salmon. These studies 

 were designed 1 ) to investigate dif- 

 ferences in toxicity and uptake 

 between the chloride and acetate 

 forms of lanthanum and cerium, 

 and 2 ) to assess optimal concentra- 

 tions and exposure times for mark- 

 ing coho salmon fry in the extremely 

 soft and slightly acidic water at 

 Capilano River Hatchery, British 

 Columbia. 



Materials and methods 



In the following experiments, lan- 

 thanum and cerium were intro- 

 duced into the rearing water of 

 coho salmon fry at Capilano River 

 Hatchery. The river water at this 

 hatchery is slightly acidic and ex- 

 tremely soft (pH=6.5; hardness as 

 CaC0 3 =3.8). Concentrated lan- 

 thanide stock solutions were me- 

 tered into the tanks at a rate of 



1 mLmin -1 and the rearing water 

 was set to flow in at a rate of 1 

 L-min -1 . The lanthanide solutions 

 and the rearing water were mixed 

 prior to delivery to the tanks con- 

 taining the fish. 



Two experiments were con- 

 ducted concurrently with coho 

 salmon fry. One hundred fry, with 

 an average initial weight of 3.2 g, 

 were placed in each 35-L experi- 

 mental tank. Experiment 1 had 4 

 treatment groups and a control 

 tank where no lanthanide was ad- 

 ministered. The lanthanide treat- 

 ments and elemental concentra- 

 tions were: 50 ugL -1 of LaCl 3 , 

 CeCl 3 , La(C 2 H 3 2 ) 3 , or Ce(C 2 H 3 2 ) 3 

 continuously for 24 days. Experi- 

 ment 2 involved 7 treatment groups: 

 50 Ug-L- 1 of La(C 2 H 3 2 ) 3 or 

 Ce(C 2 H 3 9 ) 3 continuously for a to- 

 tal of 24 treatment days; 100 ugLr 1 

 of La(C 2 H 3 2 ) 3 or Ce(C 2 H 3 2 ) 3 on 

 alternate days for a total of 12 treat- 

 ment days over a 24-day period; 150 

 Ug-L" 1 of LafC^O^ or CeCGjHgO^ 

 every third day for a total of 8 treat- 

 ment days over a 24-day period; 

 and a control tank with no lantha- 

 num or cerium. The treatment 

 days consisted of 24 hours of ex- 

 posure. Over the treatment period, 

 equal amounts of lanthanum or 

 cerium were administered to each 

 treatment group of fry at the appro- 

 priate concentration and duration. 



After completion of the lan- 

 thanide exposures, the fry were 

 provided with untreated river wa- 

 ter for 14 days prior to sampling. 

 Ten fry were randomly sampled 

 from each of the tanks, body 

 weights recorded, and the verte- 

 bral columns were removed and 

 prepared for ICP-MS analysis to 

 determine lanthanide accumula- 

 tion. The majority of flesh was dis- 

 sected away from the bony tissue 

 and any remaining traces of flesh 

 were digested with a 6% sodium 

 hypochlorite solution. The clean 



Manuscript accepted 29 October 1993 

 Fishery Bulletin 92:471-473 (1994) 



471 



