786 



Fishery Bulletin 90(4), 1992 



Up to seven tagged fish were deployed within the study 

 area at one time. One procedure was conducted on two 

 rocky reefs to determine the home ranges of Hngcod 

 during the day, night, and periods of strong current 

 which were predicted up to 14.81<;m/h (8.01<n) (Cana- 

 dian tide and current tables, Canadian Hydrographic 

 Service 1990). Six lingcod were captured, tagged, 

 released, and monitored at the original point of cap- 

 ture, either Gabriola reefs area or Valdes reefs. Their 

 geographic locations were determined on an almost 

 daily basis (the only exception being 18 April) for the 

 duration of the tag battery life. 



To determine the homing routes of displaced lingcod, 

 five males were captured, tagged, and displaced up to 

 2.8km in two opposite directions (Fig. 1). Four of the 

 five displaced fish were moved south, while one fish 

 was moved north. Because there was no information 

 on the time required for lingcod to home, the first fish 

 was moved a short distance (1 km) to allow enough time 

 to track its homeward movement. Of the remaining 

 four lingcod, one was displaced 2.2km, and three were 

 displaced 2.8km. The movements were then monitored 

 almost continuously, with occasional rest breaks, until 

 the transmitter batteries expired. Displaced fish were 

 individually tracked because they required continuous 

 monitoring. When the displaced fish were first re- 

 leased, an attempt was made to stay with the fish for 

 several hours to detect any homeward movement. 



The field schedule started with two teams each work- 

 ing 12 h on the boat for a full 24 h coverage. After the 

 first few days of field work, we changed the schedule 

 to devote our efforts to covering nighttime lingcod 

 movement (16:00-08:00). The entire study covered 21 

 tracking days during 5-27 April (only 18 April was 

 canceled due to boat problems) for a total of 336 track- 

 ing hours. When the nondisplaced fish were first re- 

 leased, an entire day was spent tracking those fish. 

 Subsequently, each fish was periodically (about 15-20 

 times/tracking day) checked for its position, which 

 allowed several tagged fish to be concurrently moni- 

 tored. The five displaced fish were followed one at 

 a time to ensure that their homing route could be 

 detected. 



On two separate dates, I conducted scuba observa- 

 tions to search for tagged lingcod and to collect infor- 

 mation not available through telemetry. When a signal 

 cannot be located, it was impossible to determine 

 whether the tag battery has died or the fish has left 

 the area; hence, I searched underwater for two tagged 

 fish in their last recorded location after the signal could 

 no longer be detected. Also, to determine the accuracy 

 of telemetric locations, I used scuba observations to 

 compare underwater positions of tagged fish with those 

 provided by telemetry. Once the directional hydro- 

 phone positioned the boat directly over the tag's signal 



I then anchored the boat, descended, and searched for 

 the tagged fish. 



Results 



Nondisplaced fish (controls) 



The six lingcod (three females and three males) tagged 

 and released at Gabriola and Valdes reefs were general- 

 ly found close to release sites during the day, night, 

 and periods of swift current. When relocated, the six 

 lingcod were essentially in the same position (latitude- 

 longitude differences were within 0.01-0.02 nmi, which 

 is the normal resolution of the LORAN unit). Thus, 

 there was no detectable difference in their home range 

 size. Fish were monitored for 12-20d (x 16.2-1- 2. 9d) 

 until the tag batteries expired. 



These telemetry findings were verified by visual 

 (scuba) resightings of two tagged lingcod. After deter- 

 mining the position of an ultrasonic tag, I later (within 

 a few minutes) observed the tagged fish sitting on the 

 bottom. These visual sightings also verified that the 

 tags were still attached to the fish. Furthermore, after 

 the signal had apparently died on two tagged fish, I 

 searched underwater and saw the two tagged lingcod 

 in their last recorded telemetry position. 



The six individual lingcod were also monitored on six 

 separate nights when the current ranged from slack 

 to 10.4 km/h (5.6kn) for a total of 50h of nighttime 

 observation. Home ranges were similar to those ob- 

 served in the day. However, signals were louder sug- 

 gesting that the fish were out in the open, i.e., not 

 under a rock (Matthews et al. 1990). 



Displaced fish (experimentals) 



The five displaced lingcod remained close to release 

 sites and did not move for several hours following 

 release (Figs. 2-6). These first few hours (both during 

 the day and night) following release may be a recovery 

 period in response to capture, handling, and tagging. 

 Subsequently, four of the five displaced fish moved 

 back to the capture site. Each fish had returned to the 

 capture site by the end of the second night following 

 release. Return trips were confined to the immediate 

 vicinity of the Gabriola and Valdes Islands study area. 



The four homing lingcod (nos. 7, 9-11) remained near 

 the release site for 4-6 h and returned to home sites 

 in 33-60h (Figs. 2-5). These four fish started their 

 homeward movements at night (20:30-06:00), and 

 movement terminated once it became light at ~06:00. 



No clear pattern was detected in the homeward 

 movement, as lingcod did not appear to follow obvious 

 features such as depth contours or currents. Homing 

 lingcod traversed depths of 5-35 m. Occasionally the 



