| Chum Salmon is a famous fish of cold water anadromous migratory species. As a valuable seafood, it has great economic value and because of their special life history and ecological status, it has significant research value. Recent intensive fishing and ecological problems have declined the chum salmon resource but stock enhancement also been developing rapidly with remarkable results. Currently, the resource enhancement is facing a major problem. Searching for a persistent, high stability, rich patterns and legible marking methods which will be suitable for mass group resource enhancement is particularly urgent. Fish otolith and its chemical marking can be well compatible with these characteristics. This paper carried out a series of basic research.During embryonic and juvenile period, different concentrations and t ime gradients of Alizarin Red(ARS) and Alizarin complexone(ALC) and different concentrations of Sr2+ were used in fluorescence marking experiments and strontium marking experiments respectively. Good results were obtained by detecting with Fluorescence microscope and EPMA. The fluorescence marking effect was quantized, accompanied with curve fitting and safety assessment, the appropriate conditions were observed. Based on these conditions, by merging the two chemical marking models into a composite marking method led to the detection of expected markings.1. To explore otolith deposition immersed in Alizarin red S of different concentrations(10 mg/L, 20 mg/L, 40 mg/L, 80 mg/L) and the time gradient(8 h, 16 h, 24 h, 32 h), as well as its marking results’ dynamic changes of different relaying days. Chum salmon at the period of eyed eggs were researched as immersing objects. This study was conducted for the protection of chum salmon with the approach of supplement for flag discharges,assessment for the releasing effects and provision for technical reference. The results showed that the sagittal and lapillus otoliths can be marked well, these all had great marking results detected with visible light and green laser light. The visible light marks were gradually weakened with the extension of sampling time and were almost disappeared at the 80 d and were preserved with a long fluorescence intensity under the green laser without any sign of abating. Fitting curves were obtained to express the relationship between the marking value and concentration for each series of time points. Combined with security assessments, the suitable group marking conditions for chum salmon otoliths at the stage of eyed eggs were drawed, by lying the eggs with ARS immersed at the concentration of 25.9 mg/L to 40 mg/L, the time of 15.6 h to 24 h and satisfied the conditions that coordinates under the curve of quadratic function Y=0.055X2-3.861X+86.9(X means time,Y means concentration). The new increased number of grain rounds were significantiy correlated with cultured days in linear shape and correlation equations of sagittal and lapillus otoliths were 0.965 and 0.924 which indicated that from eyed eggs to late larvae, chun salmon otoliths deposited both in sagittal and lapillus daily.2. To explore the Exogenous Sr2+ deposition in otolith of chum salmon embryos, 50 mg/L, 100 mg/L, 200 mg/L and 400 mg/L Sr2+ were used to immerse chum salmon embryos for 48 h and otoliths were taken to detect with Electro-Probe Microanalyzer after a culturing period of 12 d and 100 d. The results showed that obvious deep red strontium signatures could be produced in otolith of chum salmon at different concentrations of Sr2 +. The mean and extreme value of peak strontium area were not stable for the same Sr2+ dose but the lowest extreme was 35.1 times as large as the normal level. O verall the peak value of strontium increased with the immersed concentration of Sr2+. The strontium peak had no signs of abating after a culturing period of 100 d. The results also showed that strontium was gradually deposit in the otolith and had obvious hysteresis to immersion. Strontium deposition could also return to a normal level after the peak. These characteristics exactly according to the requirements of discharge tag technology and “strontium marking†was possible in chum salmon otolith with exogenous Sr2+. We tried to provide the foundation for “strontium marking†argument.3. Time gradient of 12 h, 24 h and 48 h were used to immerse young chum salmon in ARS at concentrations of 30mg/L, 60mg/L, 120mg/L and ALC at concentrations of 20 mg/L, 40 mg/L, 60 mg/L respectively and the effect of sedimentary were detected. Later research was referring to the effect of the mark ing on the otolith of embryonic research methods and evaluation criteria. The results showed that ARS and ALC could all immersed in otolith with red markings at UV detection during the juvenile period otolith similar to the embryonic period. While no markings were detected during visible light during juvenile period and marking situation of sagittal otolith and lapillus otolith were different as well. So, while marking with alizarins, the detection was prefered to fluorescence and the object was prefered to sagittal otolith. Then we estimated an appropriate ARS marking conditions during juvenile period, otoliths was approximately 40 mg/L, 24 h and with ALC was about 25 mg/L, 48 h. From a security and operational point of view, the appropriate marking dyestuff was ARS.4. Chum salmon embryos were immersed in Sr2+(100 mg/L, 200 mg/L) and ARS(20 mg/L, 40 mg/L) in succession. The result showed that under Sr detection and fluorescence detection, the markings could all be obtained and their sedimentary characteristics were consistent with a single. There was no interference between the two marking methods and the composite marking is feasible.5. The living condition tests after all immersions showed that immersed in fluorescent dyestuffs and Sr2+ at those dosages had less risk of acute drug manufacturing, mortality, changes in body length and weight while activity was not significantly different as compared to control which suggested that, to some extent, all chemical marking models in this study were safe.Before large-scale stock enhancements in those methods, some problems should be solved, e.g. dynamic changes and residues of chemical markers in marking groups and related toxicological studies. |
