Carp update — Jonah Yick IFS

CARP UPDATE How many left?

INLAND FISHERIES SERVICE CARP MANAGEMENT PROGRAM REPORT Jonah Yick

Over the last 12 months we caught 106 fish from Lake Sorell, and it now looks like there are less than 50 carp (0.2% of the original population) left in the lake. By early Spring, the barrier nets were in place to stop carp swimming to spawning areas in the wetlands and traps were set to catch carp. We also set gill nets in the marshes behind the barrier nets as an added precaution. The nets were set in strategic locations in response to the lake levels to catch mature carp looking for spawning habitat, and to catch any that got past the barriers. Seven carp were caught in the traps, with the warm weather and rising lake levels. Carp are known to respond to these environmental cues, and they start to push into the shallow marshes to look for spawning sites. The low catch rates are due to the small number of fish and low maturity levels.

Most of the carp this season were caught in gillnets set close to the edge of the lake. Trammel gillnets were the main type of gill net used for non-targeted effort because they are the best nets to catch the size range of fish. The biggest carp for the season was a female weighing 2229 grams, and had a well advanced gonad. This was the only large carp caught all season, with no other fish over 1500 grams, and the average size caught was less than 1000 grams. Quite extraordinary since these fish are now nine years old! Picture 1. The biggest carp of the 2017/18 season; a 2.2kg female caught in a trammel gill net set close to the shore.

Transmitter fish “Judas carp” were targeted throughout the 2017/18 season however they did not lead us to any groups of fish. In total, there were 16 events where transmitter fish were actively targeted with gill nets and backpack electroshockers, when found around the shallow edges of the lake. From this only five wild carp were caught. The low numbers of carp caught when targeting tracker fish and the lack of aggregations all suggest that there are not many carp left in the lake. Monthly sampling for spawning started in November, ending with a large survey in March which involved a total effort of 385 backpack electrofishing minutes, 6149 fyke net hours, and the use of fine mesh dip nets. Lots of eels and golden galaxiids were caught, but there was no sign of any small carp. Surveys were also done on Lake Crescent which involved a total effort of 210 backpack electrofishing minutes in previous spawning sites. Once again there was no sign of any carp in Lake Crescent, and the lake continues to be carp free since 2007. Downstream surveys in the Clyde River showed that carp are contained to Lake Sorell. In summary, this year gave the team a feel for what is Picture 2. The result of targeted effort using radio telemetry equipment, a gill net, and backpack electrofishing; on the left is an expired transmitter fish ahead, when trying to catch the last carp in a big lake. Fishing will need to be focused and persistent, even after long which was caught in a trammel net, as a result of pin periods without any sign of a pointing a current transmitter fish on the right. carp. Things are very positive, Figure 1. Total carp captures from Lake Sorell using all methods (2011-2018).

Figure 2. Catch per unit effort (CPUE) of nontargeted gill netting during the carp fishing season (October to March) in Lake Sorell comparing 2014/15, 2015/16, 2016/17, and 2017/18.

and the team is motivated to keep up the fishing pressure. We will use a wide range of fishing techniques, and aim to finish off any remaining carp during Spring 2018. If all goes to plan through the coming spring and summer, a limited opening of Lake Sorell to the public may be considered late in the 2018/19 trout season. The focus through winter will be following the transmitter fish looking for a chance to set the nets on them, as well as preparing gear for the upcoming season.