Pest Catfish Netting

I went out pest catfish netting on Thursday with Jeff and his son, the Bay of Plenty Regional Council contractors. They have nets that they set throughout the main infected bays in Western Lake Rotoiti and the Ohau Channel. They set them one day and check them the next so that the bycatch fish survive. They rotate the nets throughout the various sites over a week. It takes about 4 hours to check and sort all of the nets and record the data for the Waikato University scientists. They record numbers and length if there are less than 10 in a net or a length range if there are more than 10. At the moment the numbers are relatively low, in the 100s for the day, and all of the catfish are small, indicating that the netting programme is keeping the numbers down. The catfish spawning season starts in October though and this was when numbers exploded into the 10,000s last year. Catfish have been found up to the Ohau Channel weir at the channel's exit from Lake Rotorua so it is generally accepted now that catfish are inevitably already in Lake Rotorua and a potential disaster awaits. As you can see from the photos there are a range of fish caught in the nets. Most of the small dark fish are native bullies and the bigger ones are wild goldfish, or morihana, which were an important source of food and a local taonga for Te Arawa after the introduction of trout decimated native fish populations in the 19th century. The fish in Jeff's hand is a koaro, which survive in low numbers in many lakes, of which we caught about 7 altogether. These were the main native fish food source for Maori that existed in huge numbers prior to the introduction of trout. We also caught a number of koura at certain spots. The catch is tipped into a tray and the catfish are removed with pliers. Pliers are used as the catfish have a nasty sharp spine on their back and can turn their front side fins into rigid knives, which I found out to my detriment when I ignored advice and poked around in the tray, my finger coming out stuck deeply into a catfish fin. Ouch!! All by-catch fish were returned to the water unharmed and they swum away. The photo of the catfish is of a large one caught last year. Jeff has his pliers in the back of one of the smaller catfish in one of the photos of a full tray. The task of sorting the small catfish out from the other similar sized fish seemed daunting in the fuller trays but Jeff and his son did it easily. After awhile I found I could easily distinguish the catfish from the rest, more from their slightly different shape and brownish hue compared to the similar coloured and numerous bullies and the catfish's whiskers confirm the identification.