Egg distribution, reproductive parameters and spawning biomass of Blue Mackerel, Australian Sardine and Tailor off the East Coast during late winter and early spring
SARDI Food Safety and Innovation
Timothy M. Ward
Knowledge of the winter/spring spawning patterns of Blue Mackerel and Australian Sardine is needed to underpin future assessment of these stocks and to underpin the ecologically sustainable development of pelagic fish resources off the East Coast of Australia. Recent and robust estimates the population size of Blue Mackerel and Australian Sardine off the East Coast are needed to address community concerns regarding the potential ecological impacts of large scale fishing for small pelagic fishes off the East Coast. Information on the egg distribution, reproductive parameters and spawning biomass of Tailor is needed to inform future management of this iconic recreational fishing species.
1. Determine distribution and abundance of eggs and larvae of Blue Mackerel, Australian Sardine and Tailor off the East Coast during winter/spring.
2. Establish methods for estimating adult reproductive parameters of Blue Mackerel, Australian Sardine and Tailor off the East Coast during winter/spring.
3. Produce preliminary estimates of the spawning biomass of Blue Mackerel, Australian Sardine and Tailor of the East Coast during winter/spring.
Principal Investigator: Tim Ward
Key Words: Blue Mackerel, Scomber australasicus, Australian Sardine, Sardinops sagax, Tailor, Pomatomus saltatrix, Daily Egg Production Method, Kernel Density Growth Profile, Spawning Biomass, Small Pelagic Fishery, eastern Australia, Queensland, New South Wales
Summary: The spawning biomass of Blue Mackerel off eastern Australia during August-September 2014 was estimated to be ~83,300 t (95% CI = 35,100 - 165,000 t). Most estimates of spawning biomass obtained in the sensitivity analyses were mainly 50,000 t and 100,000 t. The estimate of spawning biomass should be treated with caution as adult samples were not collected during the study. Sampling intensity for estimates of egg production in the region was higher than in exploratory surveys conducted in 2003 and 2004. Current estimates of egg production and spawning area are likely to be more robust than those previously reported.
The spawning biomass of Australian Sardine off eastern Australia during August-September 2014 was estimated to be ~49,600 t (95% CI = 24,200 - 213,300 t). Most estimates of spawning biomass obtained in sensitivity analyses were between 30,000 t and 110,000 t. Credible values for only one parameter (spawning fraction) provided estimates of spawning biomass that were outside that range; this parameter was estimated with a high degree of confidence in the present study. The proportion of the adult biomass of Australian Sardine off eastern Australia that occurred outside the survey area during the survey period is unknown.
This study made some crucial technical developments (e.g. established a robust method for ageing fish eggs from field surveys) and filled several key knowledge gaps (e.g. estimates of adult reproductive parameters for Australian Sardine and Tailor off the east coast). However, further study is required to fill remaining gaps (e.g. adult parameters for Blue Mackerel off the east coast and egg production/spawning area and batch fecundity for Tailor) and those identified during the course of the project (e.g. spawning habitat and egg stages of Tailor).