A multi-model approach to evaluate the role of environmental variability and fishing pressure in sardine fisheries

Understanding the fluctuations in population abundance is a central question in fisheries. Sardine fisheries is of great importance to Portugal and is data-rich and of primary concern to fisheries managers. In Portugal, sub-stocks of Sardina pilchardus (sardine) are found in different regions: the Northwest (IXaCN), Southwest (IXaCS) and the South coast (IXaS-Algarve). Each of these sardine sub-stocks is affected differently by a unique set of climate and ocean conditions, mainly during larval development and recruitment, which will consequently affect sardine fisheries in the short term. Taking this hypothesis into consideration we examined the effects of hydrographic (river discharge), sea surface temperature, wind driven phenomena, upwelling, climatic (North Atlantic Oscillation) and fisheries variables (fishing effort) on S. pilchardus catch rates (landings per unit effort, LPUE, as a proxy for sardine biomass). A 20-year time series (1989-2009) was used, for the different subdivisions of the Portuguese coast (sardine sub-stocks). For the purpose of this analysis a multi-model approach was used, applying different time series models for data fitting (Dynamic Factor Analysis, Generalised Least Squares), forecasting (Autoregressive Integrated Moving Average), as well as Surplus Production stock assessment models. The different models were evaluated, compared and the most important variables explaining changes in LPUE were identified. The type of relationship between catch rates of sardine and environmental variables varied across regional scales due to region-specific recruitment responses. Seasonality plays an important role in sardine variability within the three study regions. In IXaCN autumn (season with minimum spawning activity, larvae and egg concentrations) SST, northerly wind and wind magnitude were negatively related with LPUE. In IXaCS none of the explanatory variables tested was clearly related with LPUE. In IXaS-Algarve (South Portugal) both spring (period when large abundances of larvae are found) northerly wind and wind magnitude were negatively related with LPUE, revealing that environmental effects match with the regional peak in spawning time. Overall, results suggest that management of small, short-lived pelagic species, such as sardine quotas/sustainable yields, should be adapted to a regional scale because of regional environmental variability.

Another mango season

Short fiction

Methodological challenges when estimating the effects of season and seasonal exposures on birth outcomes

Background Many previous studies have found seasonal patterns in birth outcomes, but with little agreement about which season poses the highest risk. Some of the heterogeneity between studies may be explained by a previously unknown bias. The bias occurs in retrospective cohorts which include all births occurring within a fixed start and end date, which means shorter pregnancies are missed at the start of the study, and longer pregnancies are missed at the end. Our objective was to show the potential size of this bias and how to avoid it. Methods To demonstrate the bias we simulated a retrospective birth cohort with no seasonal pattern in gestation and used a range of cohort end dates. As a real example, we used a cohort of 114,063 singleton births in Brisbane between 1 July 2005 and 30 June 2009 and examined the bias when estimating changes in gestation length associated with season (using month of conception) and a seasonal exposure (temperature). We used survival analyses with temperature as a time-dependent variable. Results We found strong artificial seasonal patterns in gestation length by month of conception, which depended on the end date of the study. The bias was avoided when the day and month of the start date was just before the day and month of the end date (regardless of year), so that the longer gestations at the start of the study were balanced by the shorter gestations at the end. After removing the fixed cohort bias there was a noticeable change in the effect of temperature on gestation length. The adjusted hazard ratios were flatter at the extremes of temperature but steeper between 15 and 25°C. Conclusions Studies using retrospective birth cohorts should account for the fixed cohort bias by removing selected births to get unbiased estimates of seasonal health effects.

Fishing for Eels

Poem.

Student physical activity levels during a season of sport education

The purpose of this study was to determine the extent to which sport education can provide students with sufficient opportunities for developing moderate- to-vigorous physical activity (MVPA). Nineteen seventh-grade boys (average age = 12.9 yrs.) participated in a 22-lesson season of floor hockey. For all students (both higher and lower skilled), students averaged a total of 31.6 min of MVPA during the season, or 63.2% of lesson time. Further, there was no significant difference according to skill level (33.4 min [Higher] vs. 30.4 min [Lower]), nor were there any significant differences in MVPA levels across the phases of the season.

The burning season

"Every year deliberately lit fires rage across Indonesia. They destroy pristine rainforest, endanger orangutans and contribute to climate change. A young carbon trading entrepreneur goes in search of a solution." "Dorjee Sun, a young Australian Entrepreneur, believes there's money to be made from protecting rainforests in Indonesia, saving the orangutan from extinction and making a real impact on climate change. Armed with a laptop and a backpack, he sets out across the globe to find investors in his carbon trading scheme. It is a battle against time. Achmadi, the palm oil farmer is ready to set fire to his land to plant more palm oil, and Lone's orangutan centre has reached crisis point with over 600 orangutans rescued from the fires. The Burning Season is an eco-thriller about a young man not afraid to confront the biggest challenge of our time."

Tweeting the TV event, creating ‘Public Sphericules’ : ad hoc engagement with SBS’s Go Back to Where You Came From – season two

This article uses the example of the mediatisation of Season 2 of the Australian documentary-cum-reality TV series Go Back to Where You Came From, and the associated #GoBackSBS Twitter feed, to investigate how public opinions are shaped, reshaped and expressed in new hybrid media ecologies. We explore how social media tools like Twitter can support the efforts of a TV production; provide spaces through which the public can engage ad hoc with a public event, be informed, shape their opinions and share them with others; and thus open up new possibilities for public discourse to occur. We suggest that new online public sphericules are emerging that provide spaces within which publics can engage with the cultural social and political realities with which they are confronted. In this way, we highlight the importance of mundane communication to the shaping and constant reshaping of public opinion.

The relationship between ambient ultraviolet radiation (UVR) and objectively measured personal UVR exposure dose is modified by season and latitude

Despite the widespread use of ambient ultraviolet radiation (UVR) as a proxy measure of personal exposure to UVR, the relationship between the two is not well-defined. This paper examines the effects of season and latitude on the relationship between ambient UVR and personal UVR exposure. We used data from the AusD Study, a multi-centre cross-sectional study among Australian adults (18-75 years), where personal UVR exposure was objectively measured using polysulphone dosimeters. Data were analysed for 991 participants from 4 Australian cities of different latitude: Townsville (19.3 °S), Brisbane (27.5 °S), Canberra (35.3 °S) and Hobart (42.8 °S). Daily personal UVR exposure varied from 0.01 to 21 Standard Erythemal Doses (median=1.1, IQR: 0.5–2.1), on average accounting for 5% of the total available ambient dose. There was an overall positive correlation between ambient UVR and personal UVR exposure (r=0.23, p<0.001). However, the correlations varied according to season and study location: from strong correlations in winter (r=0.50) and at high latitudes (Hobart, r=0.50; Canberra, r=0.39), to null or even slightly negative correlations, in summer (r=0.01) and at low latitudes (Townsville, r=-0.06; Brisbane, r=-0.16). Multiple regression models showed significant effect modification by season and location. Personal exposure fraction of total available ambient dose was highest in winter (7%) and amongst Hobart participants (7%) and lowest in summer (1%) and in Townsville (4%). These results suggest season and latitude modify the relationship between ambient UVR and personal UVR exposure. Ambient UVR may not be a good indicator for personal exposure dose under some circumstances.

Implications of differences in technical efficiency of fishing boats for capacity measurement and reduction

Capacity measurement and reduction is a major international issue to emerge in the new millennium. However, there has been limited assessment of the success of capacity reduction schemes (CRS). In this paper, the success of a CRS is assessed for a European fishery characterised by differences in efficiency levels of individual boats. In such a fishery, given it is assumed that the least efficient producers are the first to exit through a CRS, the reduction in harvesting capacity is less than the nominal reduction in physical fleet capacity. Further, there is potential for harvesting capacity to increase if remaining vessels improve their efficiency.

Gone Fishing

Gone Fishing is the touching story of a boy and old man coming to terms with bereavement through their shared love of fishing, and the legend of Goliath, the biggest pike ever caught! Financed by 150 film makers, Gone Fishing is a short film directed by Guerilla Film Makers Handbook Author Chris Jones. Thirteen minutes of magic that will touch and move you. The story is in part autobiographical - while growing up, director Chris Jones and his friends would often attempt to catch the legendary 'Oscar the pike', a fish that according to local myth terrorized the lake at the end of his road, the aptly named Blue Lagoon. This was the inspiration behind the legend of 'Goliath', the big fish in this even bigger tale. Think 'Jaws' but for kids...

Economic value of recreational fishing in Moreton Bay and the potential impact of the marine park rezoning

In 2009, the area of the Moreton Bay Marine Park was increased from 0.5 per cent of the Bay area to 16 per cent. During the planning process, opposition by commercial and recreational fishers alike was raised, arguing that loss of fishing grounds would lead to substantial loss in economic benefits. The commercial sector was compensated through a buyback of fishing effort, but the recreational sector received no compensation. In this paper, we develop a travel cost model to estimate the potential economic impact on the recreational sector from the marine park rezoning. The results suggest that, counter to initial claims, non-market recreational fishing benefits may have increased by between $1.3m and $2.5m a year, with a current total annual value of around $20m. Keywords: Travel cost model; Economic valuation; Moreton Bay Marine Park; Recreational fishing