The potential use of time-area closures to reduce catches of bigeye tuna (Thunnus obesus) in the purse-seine fishery of the eastern Pacific Ocean

Skipjack (Katsuwonus pelamis), yellowfin (Thunnus albacares), and bigeye (Thunnus obesus) tunas are caught by purse-seine vessels in the eastern Pacific Ocean (EPO). Although there is no evidence to indicate that current levels of fishing-induced mortality will affect the sustainability of skipjack or yellowfin tunas, fishing mortality on juvenile (younger than 5 years of age) bigeye tuna has increased, and overall fishing mortality is greater than that necessary to produce the maximum sustainable yield of this species. We investigated whether time-area closures have the potential to reduce purse-seine bigeye catches without significantly reducing skipjack catches. Using catch and effort data for 1995–2002, we identified regions where the ratio of bigeye to skipjack tuna catches was high and applied simple closed-area models to investigate the possible benefits of time-area closures. We estimated that the most optimistic and operationally feasible 3-month closures, covering the equatorial region of the EPO during the third quarter of the year, could reduce bigeye catches by 11.5%, while reducing skipjack tuna catches by 4.3%. Because this level of bigeye tuna catch reduction is insufficient to address sustainability concerns, and larger and longer closures would reduce catches of this species signficantly, we recommend that future research be directed toward gear technology solutions because these have been successful in many other fisheries. In particular, because over 50% of purse-seine catches of bigeye tuna are taken in sets in which bigeye tuna are the dominant species, methods to allow the determination of the species composition of aggregations around floating objects may be important

Configuration of anchorage holes affects fixation of the acetabular component in cemented total hip replacement - a finite element study

Our survey of current practice among UK orthopaedic surgeons shows wide variations in fixation techniques. The aim of this study is to investigate the effect of drilling different configurations of anchorage holes in the acetabulum on implant stability. To avoid variables that could incur during in-vitro testing, we used commercially-available COSMOS finite element analysis package to investigate the stress distributions, deformations, and strains on the cement mantle when drilling three large anchorage holes and six smaller ones, with straight and rounded cement pegs. The results, which are in line with our in-vitro studies on simulated reconstructed acetabulae, indicate better stability of the acetabular component when three larger holes than six smaller holes are drilled and when the necks of the anchorage holes are rounded. The longevity of total hip replacements could be improved by drilling three large anchorage holes, rather than many smaller ones, as initially proposed by Charnley

Reproductive Schedules in Southern Bluefin Tuna: Are Current Assumptions Appropriate?

Southern bluefin tuna (SBT) appear to comprise a single stock that is assumed to be both mixed across its distribution and having reproductive adults that are obligate, annual spawners. The putative annual migration cycle of mature SBT consists of dispersed foraging at temperate latitudes with migration to a single spawning ground in the tropical eastern Indian Ocean. Spawning migrations have been assumed to target two peaks in spawning activity; one in September-October and a second in February-March. SBT of sizes comparable to that of individuals observed on the spawning ground were satellite tagged in the Tasman Sea region (2003–2008) and demonstrated both migrations to the spawning grounds and residency in the Tasman Sea region throughout the whole year. All individuals undertaking apparent spawning migrations timed their movements to coincide with the second recognised spawning peak or even later. These observations suggest that SBT may demonstrate substantial flexibility in the scheduling of reproductive events and may even not spawn annually as currently assumed. Further, the population on the spawning grounds may be temporally structured in association with foraging regions. These findings provide new perspectives on bluefin population and spatial dynamics and warrant further investigation and consideration of reproductive schedules in this species

Secretariat of the Pacific Community, Noumea, New CaledoniaPreliminary examination of steepness in tunas based on stock assessment results

In this paper I describe a preliminary meta-analysis of steepness values across several age-structured tuna assessments conducted under the world’s RFMOs. The key findings are that: A range of values of steepness are estimated across the world’s tuna stocks For some stocks steepness estimates from the Beverton-Holt curve were very close to the maximum of 1 and were associated with very tight [and presumably unrealistic] estimates of statistical uncertainty. This made it difficult to conduct a reasonable meta-analysis from the Beverton-Holt based estimates. The mode of the random effects distribution for steepness from the Ricker curve was 0.80. This value was used in the reference case models for the 2011 WCPFC assessments of bigeye, yellowfin, and skipjack tuna. Further work is required towards meta-analysis of model outputs and the alternative approach to examining steepness through life history parameters may also yield useful results. In the interim I note the two key recommendations from the ISSF-funded workshop on steepness held in Rome, Italy earlier this year: The Workshop recommended that estimated values of steepness from individual assessments be treated with considerable caution. Analysts should evaluate the extent to which the stock-recruitment estimation or assumptions influence the estimates of recruitment; and The Workshop recommended that stock status advice incorporate stock assessment structural and parameter uncertainty including a range of plausible steepness values

Shark Species WCPFC-SC6-2010/EB-WP-01

The Fifth Regular Meeting of the Scientific Committee (SC5) of the Western and Central Pacific Fisheries Commission (WCPFC) in August 2009 considered the feasibility of quantitative stock assessments for sharks and recommended that preliminary assessments should proceed in parallel with development of a shark research plan to fill data gaps. This paper presents a proposed shark research plan in response to the Commission's approval in December 2009 of SC5's recommendation. An introduction to the Commission's eight current key shark species is presented, including a brief review of the history of their designation and species profiles containing information on habitat, life history and ecological risk, conservation status, current catches in the WCPO, and existing assessments or management. A review of existing fishery and biological information is then presented and data gaps are summarised. Major difficulties in the use of logsheet data for shark assessment are anticipated due to lack of data provision, as well as issues of species mis-identification, under-reporting and changes in targeting strategies. Observer data coverage, especially for longline fleets, is low and may not be representative of all areas where sharks are caught. Other commercial, research and recreational fishery data sources have some potential to inform the analyses but will require further work. Fisheryspecifi

ANALYSIS OF PURSE SEINE SET TIMES FOR DIFFERENT SCHOOL ASSOCIATIONS: A FURTHER TOOL TO ASSIST IN COMPLIANCE WITH FAD CLOSURES?

different school associations: a further tool to assist in compliance with FAD closures

WCPFC‐SC10‐2014/MI‐WP‐01

Evaluation of risks of exceeding limit reference points for south Pacific albacore, bigeye, yellowfin and skipjack tunas with implications for target reference points: a case study using south Pacific albacor