Search

A biomass dynamic model making use of an observation error estimator has been used over recent years to assess the status of the squid resource, Loligo vulgaris reynaudii, off the coast of South Africa. This assessment has indicated the resource to be at a low level and the risk of collapse under the current level of fishing effort to be high. Accordingly, past scientific management advice has been that effort should be reduced. This assessment is refined here to take account of both observation and process error, and a number of sensitivity tests related to assumptions made in the original model are conducted. Bayesian analyses to take full account of estimation uncertainty are also undertaken. The results from the respective analyses are reported, and it is shown that changing the “hockey-stick” stock–recruitment function of the original model to a Beverton–Holt form opens the possibility that the resource is under less risk from the current level of effort than has been supposed.

A decrease in somatic growth rate, and hence productivity, of the South African west coast rock lobster population which occurred in the late 1980s has had important ramifications for subsequent TACs set for this resource. These are critically dependent on monitoring growth rates and determining whether an increase back towards earlier higher levels is underway. The available data are not well balanced by season and location, and a GLMM approach is used to take account of season–location interactions by treating these as random effects. This results in much less precise estimates of annual somatic growth rate than had been suggested by an earlier fixed effects GLM approach, and has necessitated a change in the philosophy underlying management of the resource.

Increased fishing effort may downwardly bias indices of abundance, such as catch-per-unit-effort (CPUE), due to gear saturation. A field experiment was developed to assess gear-saturation effects on an index of relative abundance used for stock-assessments of rock lobster, Palinurus gilchristi , off South Africa. A progressive decrease in the value of the index, which is derived from commercial trap catch rates after accounting for the influences of vessel characteristics, trap soak-times, depth, area and month, has led to cuts in the total allowable catch (TAC) over the past 10 years. Concerns have been raised, however, that recent steep increases in fishing effort might have led to gear saturation effects, so that the index may now underestimate abundance relative to periods of lower effort, and hence the resource may not have declined to the extent that the index suggests. In the experiment, the fishing grounds were subdivided into the Agulhas Bank and Eastern fishing grounds, and both areas were subjected to three 2-month treatments of either unrestricted fishing effort or reduced fishing effort. In both areas, fishing in the first 2 months was unrestricted. In the second 2-month period, the number of trap-days was reduced by 25–30%, whereas in the third 2-month period this number was further reduced on the Agulhas Bank (by 65%), but increased by 25% on the Eastern fishing grounds. In terms of the saturation hypothesis, CPUE was predicted to rise during periods when effort was reduced. Changes in CPUE were assessed by expressing CPUE during periods of reduced effort as a proportion of CPUE during periods of unrestricted effort. These proportions were compared to proportions for equivalent time periods in previous years (1991–1998) when fishing effort was always unrestricted. The null hypothesis that CPUE is unaffected by effort (i.e. no gear-saturation effect) was rejected in only one of four treatments. In the other three treatments, the experiment failed to separate responses to effort-manipulations from those due to seasonal and areal fluctuations in catchability. However, a model that integrates the results of all four treatments suggests that, if GLM-standardized effort is used as the index of potential saturation, there is only a 2.5% probability that saturation could account for as much as 0.004 of the drop in CPUE from 0.15 to 0.09 kg tails/trap between 1991/1992 and 1997/1998. If trap-days instead are used as the saturation index, this 0.004 figure increases, but only to 0.03. This thus suggests with very high probability that saturation effects cannot alone explain the drop in CPUE in the fishery during the 1990s.

Catch per unit effort (cpue) data for the South African west coast Cape hakes Merluccius capensis and M. paradoxus were standardized by applying the Generalized Linear Modelling (GLM) technique. The resulting standardized series indicated that resource abundance declined at a rate of 0.4% per annum over the period 1978–1994. Further investigation revealed that the model applied did not adequately adjust for effort being directed away from hake towards other species. This was because, for low bycatch cpue, there was a positive rather than the expected negative correlation with hake catch rates. A method to correct for this inadequate adjustment, taking account of an assumed underlying reason of positively correlated fluctuations in catchability of hake and bycatch species, was developed and tested by simulation. This resulted in a more optimistic view of resource status, indicating a 0.6% per year increase in abundance over the period considered. This result remained contrary to general perceptions in the ...

Dermal contact with isocyanate-based coatings may lead to systemic respiratory sensitization. The most common isocyanates found in sprayed automotive coatings are monomeric and oligomeric 1,6-hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI). Most spray painters use thin (4–5 mil) latex gloves that are not effective at preventing dermal exposures when spraying isocyanate paints. Personal interviews with collision repair industry personnel and focus groups with spray painters were held to characterize risk awareness, to examine perceptions and challenges concerning protective glove use and selection, and to generate ideas for protective glove use interventions. The most popular gloves among spray painters were thin (4–5 mil) and thick (14 mil) latex. We found that medium to thick (6–8 mil) nitrile were not always perceived as comfortable and were expected to be more expensive than thin (4–5 mil) latex gloves. Of concern is the user's difficulty in distinguishing between nitrile and latex gloves; latex gloves are now sold in different colors including blue, which has traditionally been associated with nitrile gloves. Even though spray painters were familiar with the health hazards related to working with isocyanate paints, most were not always aware that dermal exposure to isocyanates could contribute to the development of occupational asthma. There is a need for more research to identify dermal materials that are protective against sprayed automotive coatings. Automotive spray painters and their employers need to be educated in the selection and use of protective gloves, specifically on attributes such as glove material, color, and thickness.