Catostylus mosaicus Port Phillip Bay Australia 1990-2010

Jellyfish were collected using a wing trawl net (47 m long, 13 m wing spread, 5 m opening height and 45 m between trawl doors) at 22 depth-stratified sites in Port Phillip Bay, Australia.. Sites were sampled once per year between late February and early April (austral summer/autumn) in all years between 1990 and 2010, except in 1998 and 2001. Sites were located in four regions of the bay: Port Phillip Bay Central (11 sites), Port Phillip Bay South (8 sites), Geelong (2 sites), Hobsons Bay (1 site). At each site, two trawl tows were undertaken, so a total of 44 tows were completed annually, although in 1994 only 43 tows were successfully completed. The data presented are the average of the two trawls taken at each site. The duration of each trawl shot was nominally 5 minutes, measured from the time load cell clamps were attached until the winch commenced the retrieval of the net. Data obtained using a netsonde indicated that the net was fishing for an additional 2 minutes during its retrieval. The speed of the net across the sea bottom was 2.1-2.5 knots. Between 1990 and 1997, sampling was undertaken by the RV Sarda, a 20 m research vessel, but from 1999 onwards sampling was undertaken by a commercial trawler, the ‘Castella Rosa’. The effect of the change in vessel on catches ws minimised by selecting a vessel of similar size to Sarda and by using Sarda’s skipper on all trawls in 1999 and 2000, and by maintaining a similar winch speed of ~1 m.s-1 on both vessels. Fish and jellyfish were sorted on deck and the number and total weight of each species was recorded.