Assessment of catches from Protective Shark meshing off NSW beaches between 1950 and 1990

Abstract

Mesh netting of beaches along the more populous sections of the NSW coast for the protection of swimmers and surfers against shark attack has been carried out since 1937 in Sydney and since 1949 in Newcastle and Wollongong. Data for the catches of sharks by taxonomic groups are presented for the period from 1950 to 1990. Although there were large year-to-year fluctuations, neither catch nor catch per unit effort showed any discernible trend for the period up to 1972. In 1973, the catches of all taxonomic groups increased substantially following changes to the specifications of nets and their deployment. Since 1974, there has been a continuing decline in both the numbers of sharks caught and the catch per unit effort. Although Carcharhinus spp. (whalers) and Carcharodon carcharias (white pointer sharks) have shown an almost unbroken decline since the commencement of meshing, Sphyrna spp. (hammerheads) and Squatina australis (angel sharks) have shown large fluctuations over the entire study period, particularly in the period following the upgrading of netting effectiveness (post-1973). Substantial changes have occurred in the size compositions of a number of the taxonomic groups between the first and second 20-year periods of the meshing programme. High proportions of S. Australis and Carcharias taurus (grey nurse sharks) were females. There were major differences in the species compositions of catches between the three major meshing areas and between the pre- and post- 1973 periods. Data on the catches of nontarget species for the Newcastle region for the period from 1965-66 to 1980-81 indicated significant increases in the catches of rays and jewfish in the post-1973 period. Post-1973 changes in the catches of dolphins, turtles and tunas were not statistically significant.

Decadal trends in shark catches and effort from the New South Wales, Australia, Shark Meshing Program 1950 - 2010

“…Additionally, fishing effort changed over the years, with contractor requirements being specified through their contracts (Green et al 2009). Reid and Krogh (1992) presented effort as the number of sets per year, whereas the current analysis investigates the effort measured as the number of days fished, which is considered a more appropriate way of presenting real effort. Although shifts in effort have complicated assessment of catch data, the overall fishing effort increased because of the addition of new beaches in the SMP until 1992.…”

“…Aside from a break of 3 years during World War II (Reid and Krogh 1992), the NSW shark nets have fished almost continuously from 1937 to the present. Because records are incomplete before 1949, the current study has focussed on meshing operations from July 1950 to April 2010 (i.e.…”

“…The use of anchored, large-mesh gill-nets as a preventative measure was pioneered in NSW, Australia, following recommendations that they may afford a 'cheap and effective way of minimising the shark peril' (New South Wales Shark Menace Committee 1929). Nets were subsequently installed off Sydney beaches in 1937 (Reid and Krogh 1992) in a program that continues today.…”

“…Although a substantial proportion of the attention that these major beach-protection programs have received has been focussed on the effects that their catches have on targeted (potentially dangerous) shark populations (Paterson 1986;Cliff and Dudley 1992;Reid and Krogh 1992;Simpfendorfer 1993;Dudley and Simpfendorfer 2006) and the populations of by-catch species (Heinsohn 1972;Paterson 1979Paterson , 1990Cockcroft 1990;Krogh 1994;Gribble et al 1998), these programs represent an extended sampling period of coastal waters in the regions they operate. Thus, they provide a reliable record of the long-term trends in abundance and distribution of regional shark species.…”

“…Changes in effort have previously been described and standardised in a review of the catch, comparing the pre-and postmajor 1972 review of the NSW Shark Meshing Program (Reid and Krogh 1992). Substantial changes to the SMP are presently being implemented in the 2010-2011 season following a new joint management agreement (JMA) among the historical custodians of the program, the NSW Department of Primary Industry (now known as Industry & Investment NSW) and the NSW Department of Environment, Climate Change and Water.…”