Fisheries long term monitoring program : summary of Spanish mackerel (Scomberomorus commerson) survey results: 2004–05

Abstract

Spanish mackerel, Scomberomorus commerson, is an important commercial and recreational pelagic fish species. It has similar total landings for both of these sectors on the Queensland east coast. The majority of the commercial landings come from the Lucinda area, north of Townsville, whilst the bulk of recreational catch comes from south east Queensland (Bundaberg to the Gold Coast).
A preliminary stock assessment of the east coast Spanish mackerel fishery suggested that the exploitable biomass in 2002 had declined to approximately 44% of the estimated unfished biomass (Welch et al. 2002). The stock assessment recommended that fishing effort should not be increased above the 2002 level. Following the assessment, Hoyle (2002) conducted a management strategy evaluation of the east coast Spanish mackerel stock. The management strategy evaluation outlined alternative management arrangements. It proposed alternative monitoring and assessment methods to improve the resolution and utility of the information being collected.
Tobin and Mapleston (2004) identified that the biological characteristics of harvested Spanish mackerel on the east coast of Queensland varied between fishing sectors and coastal regions. They found that the landed catches from the recreational sector tended to be more diverse in size and age structure. Based on Tobin and Mapleston’s findings and a management strategy evaluation of the fishery (Hoyle 2003), it was concluded that the Department of Primary Industries and Fisheries’ Long Term Monitoring Program for Spanish mackerel, which commenced in 1999, was not representative of the entire Queensland fishery.
In 2004, the Long Term Monitoring Program was expanded to collect representative length, sex, and age information from both the recreational and commercial catch of Spanish mackerel from four regions along the Queensland east coast. The program also collected information on the spatial and temporal distributions of spawning. The monitoring strategy was designed from recommendations made by Sumpton and O’Neil (2004).
In the 2004–05 financial year, Spanish mackerel data were collected from Cairns to the New South Wales border from the commercial and recreational fishing sectors. These results for the Queensland east coast indicate:
• the majority of Spanish mackerel collected in 2004–05 were between 800 and 1100 mm fork length
• a higher proportion of the recreational catch was made up of relatively small (<800 mm fork length) and large (>1200 mm fork length) Spanish mackerel compared to the commercial catch. However, the sample sizes of fish collected in the recreational and commercial sectors were not equal.
• similar numbers of male and female Spanish mackerel were sampled during the 2004–05 season.
• the majority of female fish with ovaries in spawning condition were collected between September and December 2004
• the 3% of pre-mature fish caught by the commercial fishing sector is under the 5% reference point recommended by the Australian Government Department of the Environment and Heritage.

Future monitoring will focus on increasing the number of samples collected from the recreational sector across all regions.
The data summarised in this report are the results from the first year of a revised monitoring program for Spanish mackerel. This information provides biological data suitable for the stock assessment of Spanish mackerel.