1 American shad are an endogenous fish species2 native to the eastern United States and Canada, 3 where the numbers are declining due to several factors. 4 These fish are known for being 5 a sensitive species to handling, 6 and very few tagging studies have been successful 7 in studying their behavior and survival 8 without observing high rates of mortality. 9 To aid in study in short-term movements 10 of small and sensitive fish like juvenile shad, 11 researchers at Pacific Northwest National Laboratory 12 have developed a new miniature acoustic transmitter, 13 and evaluated many steps of the tagging process, 14 including fish collection, transportation, 15 holding, tagging, and post-tagging recovery.
16 The overall goal of this study was to develop a protocol 17 for tagging juvenile American shad, 18 with an acoustic transmitter 19 that would minimize the detrimental effects of handling 20 and maximize post-tagging survival. 21 Although non-native to the Pacific Northwest, 22 American shad have become very abundant in the region. 23 Juvenile shad used in this study were collected 24 from a fish bypass facility 25 at a hydroelectric dam on the Lower Columbia River, 26 and transported to our aquatic research laboratory.
27 The recommended technique 28 for tagging juvenile American shad is a pectoral incision 29 with internal acoustic transmitter implantation, 30 without the use of sutures to close the wound. 31 This implantation technique can be performed 32 in less than 30 seconds, has a high tag retention rate, 33 and allows quick healing of the wound. 34 Other techniques that helped to minimize stress 35 and handling mortalities included 36 using water-to-water transfers 37 and holding fish in brackish salt water, 38 both prior to and after tagging.
39 When brackish salt water40 is not readily available, 41 use a static system for holding shad 42 with proper aeration and circulation, 43 for one to two days before release. 44 In a static circular tank, 45 install an airlift system to provide aeration. 46 Connect a PVC pipe such that a T is located at the top, 47 another T is at the middle, 48 and a screened fitting is threaded 49 onto the bottom of the pipe.
50 Next, connect an airstone to a compressed airline, 51 and place the airstone at the bottom of the pipe 52 near the screen. 53 The screen prevents fish from swimming 54 into the airlift system. 55 Fill the tank with fresh water 56 until the exit port of the airlift 57 is approximately halfway submerged.
58 Then, turn off the water. 59 Next, turn on the air supply 60 until the aerated water exiting the port creates 61 directional flow for fish to orient. 62 Add commercial sea salt to make 63 a 7.5 parts-per-thousand brackish salt water solution, 64 and stir until dissolved.
65 Prior to collecting fish from a holding tank, 66 prepare a bucket of salt water. 67 Measure 7.5 grams of sea salt 68 for every 0.5 liters of water. 69 Use a gloved hand to dissolve the salt in the bucket.
70 Note that in step three, 71 an equal volume of fresh water can containing the shad 72 is added to create a final concentration of 7.5 PPT. 73 In another bucket, 74 measure and dissolve 7.5 grams of sea salt 75 for every liter of water, 76 then add 120 grams tricaine-methanesulfonate 77 buffered with 120 milligrams sodium bicarbonate 78 per liter of salt water. 79 Add supplemental air to the anesthetic buckets.
80 Next, partially fill another bucket with fresh water 81 and place it sideways into the pre-tagging source tank, 82 and use a net or hand to gently guide shad 83 to swim into the bucket. 84 Once an appropriate number of fish are in the bucket, 85 turn the bucket upright and secure it with a perforated lid. 86 Pour out any excess water through the lid, 87 keeping the fish contained 88 in the target amount of fresh water.
89 Gently pour the shad and the fresh water 90 into the salt water source bucket prepared in step two. 91 Note, the final salinity will be 7.5 PPT. 92 Provide supplemental air 93 to the pre-tagged fish source bucket 94 using an aquarium air pump and airstone 95 to maintain dissolved oxygen at an acceptable level.
96 Disinfect transmitters in 70%ethanol for 20 minutes, 97 and rinse with sterile water before use. 98 Then, using a dip net with smooth extra fine mesh, 99 net a fish from the source bucket 100 and into the anesthetic bucket. 101 Shad should lose equilibrium and spinal reflexes 102 in about two to three minutes.
103 Once fully anesthetized, use a gloved hand 104 to gently place the fish on a wet measuring board 105 to obtain its length. 106 Move the fish into a water-filled weight boat 107 on a teared scale to obtain its weight. 108 Record length and weight, acoustic tag code, 109 and any comments on the fish's condition prior to tagging, 110 such as scale loss or hemorrhaging.
111 Next, place the fish in a transfer container 112 filled with anesthetic salt water, 113 and deliver it along with the acoustic transmitter 114 to the fish surgeon. 115 Place the fish left side facing down 116 on a wet water-resistant foam pad 117 prepared with a V groove. 118 Supply fresh water to the fish's mouth 119 via tubing attached to a gravity fed water reservoir.
120 Using a disinfected 121 or brand new number 11 stainless steel surgical blade, 122 make a three-millimeter-long incision, 123 vertically, between the myomeres 124 near the distal end of the pectoral fin. 125 Carefully insert the transmitter into the incision, 126 and push it posteriorly 127 until the entire tag rests inside the body cavity. 128 If needed, use the blunt end of the scalpel, 129 or a fine-tipped forceps, to carefully insert the tag fully.
130 Next, place the tagged fish in a small container 131 of 7.5 PPT salt water with aeration, 132 to allow the fish to recover from anesthesia. 133 Once the fish has regained equilibrium, 134 make a water-to-water transfer from the recovery container 135 to the post tagging holding tank containing salt water. 136 Allow tagged fish to recover in salt water 137 for one to two days prior to release.
138 The laboratory evaluations demonstrated 139 that juvenile shad survival and tag retention were highest 140 when fish were implanted 141 with the pectoral incision location, 142 compared to other tagging techniques 143 that included gastric insertion, 144 pelvic incision, and dorsal attachment. 145 Survival for tagged fish in this evaluation was defined 146 as both survival and tag retention, 147 because tag expulsion cannot be differentiated 148 from a mortality event in a telemetry study. 149 This figure shows the P 5 dummy transmitter used 150 in laboratory evaluations, 151 and the prototype acoustic transmitter 152 with functional components.
153 The final prototype transmitter is 154 approximately 7.6 millimeters long, 155 2.0 millimeters in diameter, 156 and has a weight and air of about 50 milligrams. 157 This figure illustrates the 60-day survival 158 for one tank of juvenile shad 159 tagged with the P5 transmitter, 160 compared to the untagged control group. 161 The 60-day survival was 81.5%for the tagged group, 162 and 70%for the untagged controls.
163 There was no statistical difference in survival 164 between the two groups, 165 however, the power to detect a difference was 38.4%166 We developed a detailed handling and tagging protocol167 that will be useful in studying small, 168 sensitive and threatened fish species such as American shad. 169 We found that minimizing out-of-water handling 170 and the use of brackish saltwater pre and post-tagging 171 improved survival of these fish. 172 The results of these evaluations demonstrate 173 that the survival of tagged shad was comparable 174 to the survival of untagged shad, beyond the duration 175 of the acoustic transmitter's battery life, 176 which is expected to be about 30 days 177 with a five-second ping rate interval.
178 This technology will allow researchers179 to gain valuable information on juvenile shad behavior 180 near hydro facilities, 181 and determine route-specific survival rates. 182 The results gain from inRiver's studies can better inform 183 management decisions at these facilities, 184 to improve passage and survival rates of juvenile fish. 185 In addition, these techniques are easily transferable 186 to implanting shad with passive integrated transponder tags, 187 which can provide long-term monitoring 188 throughout their life history.
