The biological indicators and temporal spawning habits of wrasse (Family: Labridae) from Sunnhordland
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The salmonid industry in Norway has grown exponentially. The greatest cost and danger to the salmonid industry are ectoparasitic sea lice (Lepeophtheirus salmonis). Sea lice attach to salmon causing damage and increasing health risks. Wrasse (Family: Labridae) provide a possible solution. Wrasse, specifically ballan, corkwing, goldsinny, and rock cook, are cleaner fish. They can be released into sea pens and will eat the sea lice off the salmon. This has been highly effective against sea lice. As a result wrasse have gone from a worthless fish (bony and not particularly tasty) to a highly desired multi-million kroner fishery. The growth of the fishery raises serious concerns. As a result of wrasse being unimportant until recently little information is known about them, including their reproductive habits. To provide further information regarding spawning and the stock of wrasse this project was developed to study the four economically important wrasse: ballan, corkwing, goldsinny, and rock cook. Over the space of two months in the spring/summer of 2014 I regularly participated in fishing expeditions with wrasse fisherman and research staff. The goal was to get a picture of the wrasse stock in Sunnhordaland and multiple sites were targeted. Data were collected in Austevoll (21 dates), Os (2 dates) and Sveio (3 dates). These 26 separate trips produced 4985 wrasse that were catalogued at sea. Of these, a sub-sample of 818 were euthanized and taken to the lab for analysis. Data on place, date, length, sex (when possible), and spawning behavior were collected on all fish observed in the field. There were a number of analyses done with the primary interest being first to accurately map the spawning patterns across the summer and to see how spawning behavior differed by species, size (length), across time and place, and by sex. The second dependent variable considered was sexual maturity. Most of these analyses required using the laboratory facilities for the sub-sample brought to the Institute for Marine Research in Austevoll. In the laboratory these 818 fish were dissected to extract the gonads to determine both sex and whether the individual was sexually mature. Furthermore otolith dating was used to determine the age of each individual fish. The spring of 2014 was warmer than average so spawning had already started for most species by the time I started collecting data in early May. Broadly speaking the data show spawning rising throughout May and into June, but then tapering off near the end of June and into July. As such the opening of the 2015 wrasse season for test fishing on July 1st seems appropriate. In looking at the individual fish the patterns are largely consistent with the literature. There were some findings, however, that indicate there may be some stress on the stock. Chief among these were findings that both corkwing wrasse and goldsinny were noticeably smaller in size at maturity than what was predicted by the literature.