UNDER-REPORTING OF CATCHES OF SOUTH COAST ROCK LOBSTER PALINURUS GILCHRISTI, WITH IMPLICATIONS FOR THE ASSESSMENT AND MANAGEMENT OF THE FISHERY

Abstract

Under-reporting of fishery catches can severely affect the precision of stock assessment estimates, which require accurate information on catch and catch rate. Under-reporting of catches of South Coast rock lobster Palinurus gilchristi over the past decade was estimated from verified daily catch rates and the number of days spent at sea by the commercial fleet. The malpractice increased sharply between the 1997/98 and 2000/01 fishing seasons. The index of abundance for the resource (standardized catch per unit effort) increased by 2% for 1998/99, 12% for 1999/00 and 14% for 2000/01, after eliminating under-reported information from the input data. An agestructured production model, with the adjusted abundance index as an input, and including known and estimated over-catches between 1991/92 and 2000/01, increased the maximum sustainable yield estimate from 360 to 390 tons tail mass. The Total Allowable Catch (TAC) management regulation that was historically used in the fishery failed to address over-harvesting as a result of poor compliance. A combined TAC and Total Allowable Effort management strategy was introduced in 2000/01 to restrict fishing effort (days at sea) on the basis of quota size and vessel efficiency. Changes in management strategy, which include cancellation of the license of a fishing company responsible for systematic under-reporting and over-harvesting, decrease in fishing effort, reduction in over-capacity of vessels and other infrastructure and stabilization of trap catch rates have improved the outlook for the fishery.