Oral Presentation Australian Society for Fish Biology Conference 2017

Cruising along or collapsing: what is the status of WA’s last cobbler fishery? (#29)

Kim Smith 1 , Alex Hesp 1 , Norm Hall 1 , Ainslie Denham 1
  1. WA Department of Fisheries, NORTH BEACH, WA, Australia

Prior to 1980, cobbler (Cnidoglanis macrocephalus) was an important commercial fishery species in southern estuaries in WA, with a combined annual catch of several hundred tonnes.  Fishing pressure and habitat degradation led to stock declines in several estuaries.  The biological characteristics (e.g. low fecundity, high parental care/nest guarding, specific habitat requirements, small discrete populations in each estuary) make cobbler inherently vulnerable to these threats. Today only one WA estuary, Wilson Inlet, continues to host a significant cobbler fishery. 

In Wilson Inlet, a relatively large amount of fishery-dependent and -independent information has been collected since the 1980s (catch sampling, juvenile surveys, tagging, etc). Key indicators now strongly suggest the current stock status is unacceptable: i) declining recruitment; ii) very high mortality with increasing trend; iii) highly truncated age and length structure with increasing trend.  Retrospective SPR estimates suggest the spawning stock level has been below 20% for at least a decade. However, despite the apparently dire state of the stock, the catch and commercial CPUE has remained stable for 3 decades. Why?

We discuss the lines of evidence and analyses used in the latest assessment, including sources of uncertainty that are common to many fishery assessments.