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Electronic monitoring (EM) is increasingly used to monitor catch and bycatch in wild capture fisheries. EM video data are still manually reviewed and adds to ongoing management costs. Computer vision, machine learning, and artificial intelligence-based systems are seen to be the next step in automating EM data workflows. Here we show some of the obstacles we have confronted and approaches taken as we develop a system to automatically identify and count target and bycatch species using cameras deployed to an industry vessel. A Convolutional Neural Network was trained to detect and classify target and bycatch species groups, and a visual tracking system was developed to produce counts. The multiclass detector achieved a mean average precision of 53.42%. Based on the detection results, the visual tracking system provided automatic fish counts for the test video data. Automatic counts were within two standard deviations of the manual counts for the target species and most times for the bycatch species. Unlike other recent attempts, weather and lighting conditions were largely controlled by mounting cameras under cover.

International audience; 1. Many animal taxa exhibit sex-specific variation in ecological traits, such as foraging and distribution. These differences could result in sex-specific responses to change, but such demographic effects are poorly understood. 2. Here, we test for sex-specific differences in the demography of northern (NGP, Macronectes halli) and southern (SGP, M. giganteus) giant petrels-strongly sexually size-dimorphic birds that breed sympatrically at South Georgia, South Atlantic Ocean. Both species feed at sea or on carrion on land, but larger males (30% heavier) are more reliant on terrestrial foraging than the more pelagic females. Using multi-event mark-recapture models, we examine the impacts of long-term changes in environmental conditions and commercial fishing on annual adult survival and use two-sex matrix population models to forecast future trends. 3. As expected, survival of male NGP was positively affected by carrion availability, but negatively affected by zonal winds. Female survival was positively affected by meridional winds and El Niño-Southern Oscillation (ENSO), and negatively affected by sea ice concentration and pelagic longline effort. Survival of SGPs did not differ between sexes; however, survival of males only was positively correlated with the Southern Annular Mode (SAM). 4. Two-sex population projections indicate that future environmental conditions are likely to benefit giant petrels. However, any potential increase in pelagic longline fisheries could reduce female survival and population growth. 5. Our study reveals that sex-specific ecological differences can lead to divergent responses to environmental drivers (i.e. climate and fisheries). Moreover, because such effects may not be apparent when all individuals are considered together, ignoring sex differences could underestimate the relative influence of a changing environment on demography. K E Y W O R D S giant petrels, Macronectes giganteus, Macronectes halli, sex-specific effects, sexual size dimorphism, South Georgia, Southern Ocean, survival

1.Incidental mortality (bycatch) in fisheries remains the greatest threat to many large marine vertebrates and is a major barrier to fisheries sustainability. Robust assessments of bycatch risk are crucial for informing effective mitigation strategies, but are hampered by missing information on the distributions of key life‐history stages (adult breeders and non‐breeders, immatures and juveniles). 2.Using a comprehensive biologging dataset (1,692 tracks, 788 individuals) spanning all major life‐history stages, we assessed spatial overlap of four threatened seabird populations from South Georgia, with longline and trawl fisheries in the Southern Ocean. We generated monthly population‐level distributions, weighting each life‐history stage according to population age structure based on demographic models. Specifically, we determined where and when birds were at greatest potential bycatch risk, and from which fleets. 3.Overlap with both pelagic and demersal longline fisheries was highest for black‐browed albatrosses, then white‐chinned petrels, wandering and grey‐headed albatrosses, whereas overlap with trawl fisheries was highest for white‐chinned petrels. 4.Hotspots of fisheries overlap occurred in all major ocean basins, but particularly the south‐east and south‐west Atlantic Ocean (longline and trawl) and south‐west Indian Ocean (pelagic longline). Overlap was greatest with pelagic longline fleets in May–September, when fishing effort south of 25°S is highest, and with demersal and trawl fisheries in January–June. Overlap scores were dominated by particular fleets: pelagic longline—Japan, Taiwan; demersal longline and trawl—Argentina, Namibia, Falklands, South Africa; demersal longline—Convention for Conservation of Antarctic Marine Living Resources (CCAMLR) waters, Chile, New Zealand. 5.Synthesis and applications. We provide a framework for calculating appropriately weighted population‐level distributions from biologging data, which we recommend for future fisheries bycatch risk assessments. Many regions of high spatial overlap corresponded with high seabird bycatch rates recorded by on‐board observers, indicating that our approach reliably mapped relative bycatch risk at large spatial scales. Implementation of effective bycatch mitigation in these high‐risk regions varies considerably. Although potential bycatch risk appears to have decreased since the early 2000s, albatross and petrel populations from South Georgia and elsewhere are still declining, emphasizing the need for much improved observer coverage and monitoring of compliance with bycatch regulations.

Patagonian grenadier (Macruronus magellanicus) is the most abundant demersal fisheries resource off Chilean Patagonia, and also is a key fisheries species off the south of Argentina and off the Falkland Islands. A Stock Synthesis assessment shows that this stock has declined in abundance off Chile, which has been attributed to a major change in recruitment strength, and subsequent production, after 1999. An assessment is conducted in which the change in recruitment is modelled as a shift in the stock-recruitment relationship. Management Strategy Evaluation is then used to examine the consequences of a mismatch between the assumptions related to recruitment in the assessment used to set the annual total allowable catch (TAC), and those in the operating model that represents the actual situation being managed. A management strategy that does not consider a shift in recruitment resulted in average TAC values of approximately 125,000 t, substantially larger than the sustainable yield of 45,000 t when there is a recruitment shift. A management strategy based on ignoring the shift in recruitment would thus lead to unsustainable catches, with major impacts on the ecosystem as well as the industry and coastal communities reliant on the fishery, if there was an actual shift in recruitment. Management of the fishery has not accounted for a recruitment shift, and annual landings have been consistently lower than the estimated annual TACs. The 2014 landings are similar to the long term TAC estimated by the assessment models under the Shift operating model. The history of the Patagonian grenadier fishery demonstrates the benefits of taking a precautionary approach that accounts for changes in fish productivity (whether climate-driven or otherwise). However, there can be considerable delays before a shift is observed in recruitment estimates or assessment model mis-specification is detected. The need for alternative approaches for providing more timely recruitment information is discussed.

There is a need to provide quantitative measures of uncertainty to support fisheries management decision making. A retrospective analysis of historical assessments for fish stocks off southeast Australia is conducted to quantify the extent of uncertainty associated with estimates of spawning stock biomass in absolute terms and when expressed relative to spawning stock biomass over a sequence of reference years. This approach to quantifying uncertainty captures more sources of uncertainty than alternative approaches, such as the estimate of the variance of terminal year spawning stock biomass from asymptotic methods, the extent to which estimates of spawning stock biomass vary among the sensitivity tests that form part of most assessments, and conventional retrospective analyses. By all measures, estimates of spawning stock biomass in absolute terms are much less certain than estimates of relative stock size (i.e. spawning stock biomass relative to a reference level), although application of most current harvest control rules rely on estimates of biomass in absolute terms. Overall, uncertainty in estimates of spawning biomass in absolute terms can be represented as a log-scale standard error of 0.37, while this standard error is 0.18 for estimates of spawning biomass in relative terms. There is considerable variation in among-assessment uncertainty in stock assessment outputs across species groups, with, for example, higher variation for assessments of chondrichthyans compared to other species.

Simulation is used to explore the effect of spatial heterogeneity and spatial closures on the ability of feedback-control management strategies to achieve goals relating to conservation and utilization of fishery resources. The operating model underlying the projections is based on pink ling, Genypterus blacodes, off southern Australia and assumes that animals are sedentary following settlement. The management strategies are able to move the resource towards the target level in the absence of spatial closures even though assessment results are biased. The probability of reducing the stock below its limit reference point is higher when growth rates vary spatially, but the effect is small. The probability of the stock being above its target reference point is lower when one of the smaller spatial areas is closed. However, performance is markedly different when a larger fraction of the total area is closed, with stock size being substantially larger than the target at the end of the projection period.

Simulation is used to evaluate the ability of a two-region, age-structured assessment model to provide accurate and precise estimates of stock status (i.e., the ratio of female spawning biomass to unfished female spawning biomass) for coral trout (Plectropomus leopardus) on the Great Barrier Reef (GBR), Australia. The model used to generate the simulated data used by the assessment model is a spatially complex age- and sex-structured population dynamics model that captures the protogynous nature of coral trout. Stock status is underestimated (negatively biased), with the extent of negative bias related to mis-specification of the breeding strategy of the target fish stock, the impact of the amount of larval connectivity among reefs, the number of reefs closed to fishing, as well as exploitation rates. The estimates of stock status were less negatively biased when fishery-independent index and age- and length-composition data were available from closed areas. The results will inform the development of management strategies for coral trout in the GBR and highlight the importance of basing evaluations of estimation and management performance on operating models that capture ecologically important processes such as metapopulation dynamics and protogynous life history.

Climate change is projected to continue shifting the distribution of marine species, leading to changes in local assemblages and different interactions with human activities. With regard to fisheries, understanding the relationship between fishing fleets, target species catch per unit effort (CPUE), and the environment enhances our ability to anticipate fisher response and is an essential step towards proactive management. Here, we explore the potential impact of climate change in the southern Indian Ocean by modelling Japanese and Taiwanese pelagic longline fleet dynamics. We quantify the mean and variability of target species CPUE and the relative value and cost of fishing in different areas. Using linear mixed models, we identify fleet-specific effort allocation strategies most related to observed effort and predict the future distribution of effort and tuna catch under climate change for 2063–2068. The Japanese fleet's strategy targets high-value species and minimizes the variability in CPUE of the primary target species. Conversely, the Taiwanese strategy indicated flexible targeting of a broad range of species, fishing in areas of high and low variability in catch, and minimizing costs. The projected future mean and variability in CPUE across species suggest a slight increase in CPUE in currently high CPUE areas for most species. The corresponding effort projections suggest a slight increase in Japanese effort in the western and eastern study area, and Taiwanese effort increasing east of Madagascar. This approach provides a useful method for managers to explore the impacts of different fishing and fleet management strategies for the future.

Model-based stock assessments form a key component of the management advice for fish and invertebrate stocks worldwide. It is important for such assessments to be peer-reviewed and to pass scientific scrutiny before they can be used to inform management decision making. While it is desirable for management decisions to be based on quantitative assessments that use as much of the available data as possible, this is not always the case. A proposed assessment may be found to be unsatisfactory during the peer-review process (even if it utilizes all of the available data), leading to decisions being made using simpler approaches. This paper provides a synthesis across seven jurisdictions of the types of diagnostic statistics and plots that can be used to evaluate whether a proposed assessment is ‘best available science’, summarizes several cases where a proposed assessment was not accepted for use in management, and how jurisdictions are able to provide management advice when a stock assessment is ‘rejected.’ The paper concludes with recommended general practices for reducing subjectivity when deciding whether to accept an assessment and how to provide advice when a proposed assessment is rejected.

In sports leagues that use an annual draft to assign eligible players to clubs, having a value associated with a draft selection can allow clubs to anticipate future growth of players and, if a trading period exists, assist negotiations when exchanging draft selections and players. Typically, mean draft values often decline in either an exponential or geometric manner with increasing draft selection number. Aggregate mean values have been used to compare trade packages. However, clubs may also want to ensure that a trade does not increase the probability of obtaining poor players in the draft. This paper therefore considers equivalence of risk as an alternative trading strategy for club list managers. Here, risk is defined as the probability of the aggregate value of the received draft selections being below a minimum acceptable level. For risk equivalence, a premium over and above mean market value may need to be provided when trading to secure higher draft selections.

An industry-based acoustic observation program was developed and applied to the austral winter spawning blue grenadier fishery from 2002. Blue grenadier has the highest Total Allowable Catch (TAC) among fished stocks of Australia’s Southern and Eastern Scalefish and Shark Fishery (SESSF). High recruitment variability and stock size uncertainty motivated development of an industry-based cost-effective acoustic monitoring program in 2002 to optimise harvest while ensuring sustainability. The development of industry-based acoustic methods resulted in “routine” surveying being carried out by skippers on industry vessels since 2006. During this time an incentive based management approach was introduced by allocation of research quota to assist in the long term implementation and delivery of the biomass indicator. The survey strategy of the industry-based method differed significantly from chartered vessel based surveys; fishers were tasked with recording the maximum biomass during the spawning season. This monitoring method shifted the “burden of proof” to industry and reinforced the need for both local and broad scale surveys to estimate the stock size. Survey results have been used for management advice by reducing uncertainty in stock size, inclusion in the stock assessment model and informing spatial planning for the region. An associated outcome was the confidence by industry that fishers’ observations of the spawning biomass were recorded and used in the stock assessment process for management of the fishery.

Spatial structure in biological characteristics and exploitation rates impact the performance of stock assessment methods used to estimate the status of fish stocks relative to target and limit reference points. Spatially-structured stock assessment methods can reduce the bias and imprecision in the estimates of management-related model outputs. However, their performance has only recently been evaluated formally, in particular when some of the area fished is closed. In order to evaluate the effects of closed areas and spatial variation in growth and exploitation rate when estimating spawning biomass, a spatially-explicit operating model was developed to simulate spatial data, and five configurations of the stock assessment package Stock Synthesis (three of which were spatially structured) were applied. The bias in estimates of spawning stock biomass associated with spatially-aggregated assessment methods increases in the presence of closed areas while these biases can be reduced (or even eliminated) by applying appropriately constructed spatially-structured stock assessments. The performance of spatially-aggregated assessments when estimating spawning stock biomass is found to depend on the interactions among spatial variation in growth, in exploitation rate, and in knowledge of the spatial areas over which growth and exploitation rate are homogeneous.

The ability to detect ecological regime shifts in a data-limited setting was investigated, using southeast Australian ecosystems as a model. Community variability was summarized for 1968–2008 with the first two principal components (PCs) of recruitment estimates for six fish stocks and reproductive parameters for four seabird species; regional climate was summarized for 1953–2008 with the first two PCs for three parameters (sea surface temperature [SST], sea surface salinity, surface nitrate) measured at two stations; and basin-scale climate variability was summarized for 1950–2012 with mean South Pacific SST and the first two PCs of detrended South Pacific SST. The first two biology PCs explained 45% of total community variability. The first two PCs of basin-scale SST showed abrupt shifts similar to “regime” behavior observed in other ocean basins, and the first PC of basin-scale SST showed significant covariation with the first PC of regional climate. Together, these results are consistent with the strong community variability and decadal-scale red noise climatic variability associated with Northern Hemisphere regime shifts. However, statistical model selection showed that the first two PCs of regional climate and the first PC of biology time series all exhibited linear change, rather than abrupt shifts. This result is consistent with previous studies documenting rapid linear change in the climate and biology of southeast Australian shelf ecosystems, and we conclude that there is no evidence for regime shift behavior in the region’s ecology. However, analysis of a large set of previously-published biological time series from the North Pacific (n = 64) suggests that studies using fewer than ∼30 biological time series, such as this one, may be unable to detect regime shifts. Thus we conclude that the nature of ecological variability in the region cannot be determined with available data. The development of additional long-term biological observations is needed for understanding change in southeast Australia and in many other marine ecosystems globally.

Three dominant recruitment patterns were identified across 30 stocks from Australia, New Zealand, Chile, South Africa, and the Falkland Islands using data from 1980 to 2010. Cluster and dynamic factor analysis provided similar groupings. Stocks exhibited a detectable degree of synchrony among species, in particular the hakes and lings from Australia, New Zealand, Chile, and South Africa. We tested three climate indices, the Interdecadal Pacific Oscillation (IPO), Southern Annular Mode (SAM), and Southern Oscillation Index (SOI), to explore their relationship with fish stock recruitment patterns. The time series of IPO and SOI showed the strongest correlation with New Zealand hoki (blue grenadier, Macruronus novaezelandiae) and Australian jackass morwong (Nemadactylus macropterus) (r = 0.50 and r = –0.50), and SAM was positively related to Australian Macquarie Island Patagonian toothfish (Dissostichus eleginoides) (r = 0.49). Potential linkages in recruitment patterns at sub-basin, basin, and multibasin scales and regional and global climate indices do account for some of the variation, playing an important role for several key Southern Hemisphere species.

The Australian Football League's (AFL's) Father–Son rule is a unique player drafting rule that allows sons of former players to be selected by their father's club. The rules that determine eligibility have undergone numerous changes since its introduction in 1949, including rules for new teams from outside of the traditional Victorian-based clubs that had no history of fathers from which Father–Son selections could be derived. The observed number of Father–Son selections to each club is markedly different between the Victorian-based clubs, and between the Victorian and non-Victorian-based clubs. In this paper, a demographic model and player data from the AFL and the state leagues are used to estimate the annual number of available sons to each of the AFL clubs. Results show that the observed number of selections can largely be explained by the number of available sons. The model can also be used to predict the number of available sons into the future, and so can be used to guide management decisions regarding competitive balance if further modifications to the AFL's Father–Son rule are required.

Populations of flesh-footed shearwaters on Lord Howe Island, Tasman Sea, have declined recently, with mortality in longline fisheries likely to be one of the major causes. It is therefore imperative to increase our understanding of their distribution at sea, especially during winter. Although they are known to migrate to the north Pacific Ocean, until this study there was very little information available on timing of movements, distribution and habitat use of individuals. Ten to 16 flesh-footed shearwaters (37 in total) were tracked from Lord Howe Island in each of three winter seasons (2005, 2007 and 2008). All birds migrated to the north-west Pacific Ocean, with approximately 70% wintering to the east of Japan in the Kurashio and Oyashio currents, around the Bonin Islands in the north Philippine Sea, or in the eastern Sea of Japan. Others spent a varying amount of time in the Yellow and East China seas, or in the western Sea of Japan. These waters already support intensive fisheries and demand for seafood is likely to rise in tandem with the increasing human populations of East Asia. Consequently, results presented here show that members of the largest population of flesh-footed shearwaters winter exclusively in the north-west Pacific Ocean around Japan and East Asia, in areas they are likely to overlap extensively with a number of fisheries; it is therefore imperative to obtain more information on current and projected levels of bird bycatch and effort in these fisheries in order to developing management strategies for the conservation of the east Australian and New Zealand populations of the flesh-footed shearwater.

Modern statistical fishery stock assessment models rarely account for temporal variability in mean length-at-age, and almost never describe cohort-specific effects. This study employs techniques for discerning temporal change to mean length-at-age from fisheries data and introduces recently developed stock assessment methods to account for this variability. Using Stock Synthesis, a statistical catch-at-age modelling framework, a stock assessment to account for cohort-specific variability in mean length-at-age was developed for blue grenadier, Macruronus novaezelandiae, an important commercial species in Australia's Southern and Eastern Scalefish and Shark Fishery. Key outputs of a standard stock assessment model that assumes static growth were compared to those of an alternative model that accounts for observed variability in length-at-age. Comparisons show that accounting for variable growth provides a better fit to time-series data and results in significant differences to key population estimates. These differences have implications for the estimation of quantities important to management and thus to scientific advice regarding recommended catch levels.

Tuck, G. N., Phillips, R. A., Small, C., Thomson, R. B., Klaer, N. L., Taylor, F., Wanless, R. M., and Arrizabalaga, H. 2011. An assessment of seabird–fishery interactions in the Atlantic Ocean. – ICES Journal of Marine Science, 68: 1628–1637. Currently, 17 of 22 albatross species are listed as Vulnerable, Endangered, or Critically endangered by the International Union for the Conservation of Nature (IUCN). Incidental mortality in fisheries is by far the most widespread cause of the population declines observed for these and other closely related species. In 2006, the International Commission for the Conservation of Atlantic Tunas (ICCAT) requested an assessment of the threat from their fisheries to all seabirds that breed or forage within their jurisdiction. Methods were developed to assess the potential consequences of fishing for more than 60 populations of seabird. The assessment framework involved the identification of at-risk populations, overlap analyses, estimation of total bycatch, and an evaluation of the impact of the bycatch on key selected populations for which there were sufficient data on bird distribution and demography. These were the wandering and black-browed albatrosses of South Georgia and the Atlantic yellow-nosed and Tristan albatrosses of Gough Island. Summary results from the seabird assessment are presented, revealing that ICCAT longline fisheries catch substantial numbers of seabirds, with potentially significant conservation implications. If this mortality is not reduced, the numbers of breeding birds in some populations will continue to decline, threatening their long-term viability.

Seabird bycatch in oceanic and coastal fisheries is believed to be the principal cause of the population declines that have been observed for many seabird populations. Pelagic and demersal longline and trawl operations have been implicated in these declines. Many government and national fishery bodies have environmental and fishery legislation that requires fisheries to be managed in a manner that is not harmful to non-target species, including seabirds. A common tool for measuring the impact of a fishery on incidentally caught seabirds is an estimate of the bycatch rate. Unfortunately, the estimation and interpretation of bycatch rates is not trivial and is complicated by poor observer coverage, under-reporting of bycatch and data lacking species specificity. In this paper, a stochastic simulation model of two seabird populations affected by a single fishing fleet is presented. The model is used to explore the consequences of applying a bycatch rate management control rule to assess and manage the fishery's incidental mortality of seabirds. Comparisons are also made with values derived from Potential Biological Removal (PBR) theory. Results conclude that using bycatch rates as a measure to assess performance of the fishery and to reduce bycatch is, under many circumstances, not sufficient to achieve conservation goals. Bycatch rates can be within the limit recommended by management, giving the impression that the fishery has reduced bycatch to sustainable levels, when in fact the low rates are due to the populations having collapsed. The interpretation of bycatch rates, and any subsequent bycatch rate management rules, needs to be considered with respect to changes in fishing effort, to population-specific impacts, to levels of compliance, and to the robustness of the bycatch rate estimate. Simply applying a bycatch rate control rule without caution can lead to catastrophic results for incidentally caught populations of seabirds.

Little, L. R., Wayte, S. E., Tuck, G. N., Smith, A. D. M., Klaer, N., Haddon, M., Punt, A. E., Thomson, R., Day, J., and Fuller, M. 2011. Development and evaluation of a cpue-based harvest control rule for the southern and eastern scalefish and shark fishery of Australia. – ICES Journal of Marine Science, 68: 1699–1705. Many fishery management agencies are adopting harvest control rules (HCRs) to achieve harvest policies and management objectives. HCRs, however, often require data-intensive stock assessments to facilitate the harvest prescription. An HCR based on catch and catch per unit effort (cpue) was developed for the southern and eastern scalefish and shark fishery of Australia, for stocks that lack the data needed to conduct a full statistical catch-at-age assessment. The HCR produces a recommended biological catch and is characterized by two parameters, target cpue and target catch, both derived from historical data. Simulation tests showed that the HCR could guide the stock to the desired state from different initial levels of depletion. However, the selection of parameter values for the HCR was critical. Achieving fishery objectives was difficult when the target catch was a function of recent catch, rather than data from a predefined historical reference period. Problems may also arise when specifying the reference period on which the HCR parameters are determined. The cpue-based HCR is a valuable tool for managing fisheries where monitoring and assessment activities are relatively expensive, or in general, where data are scarce.

Fisheries are increasingly adopting ecosystem approaches to better manage impacts on non-target species. Although deliberate dumping of plastics at sea is banned, not all fisheries legislation prohibits discarding of gear (hooks and line) in offal, and compliance is often unknown. Analysis of a 16 year dataset collected at South Georgia indicated that the amount of gear found in association with wandering albatrosses was an order of magnitude greater than in any other species, reflecting their wider foraging range and larger gape. Unlike other taxa, most gear associated with grey-headed albatrosses was from squid and not longline fisheries, and mistaken for natural prey rather than the result of direct interaction. Observed rates of foul-hooking (entanglement during line-hauling) were much higher in giant petrels and wandering albatrosses than black-browed albatrosses, and no grey-headed albatross was affected. The index of wandering albatross gear abundance showed two peaks, the most recent corresponding with a substantial increase in the number of multifilament snoods (gangions), suggesting that the widespread adoption of a new longline system (Chilean mixed) may have been responsible. Although all identified gear was demersal, given the widespread use of similar hooks, little could be assigned to a specific fishery. Stomach content analysis suggested that 1300–2048 items of gear are currently consumed per annum by the wandering albatross population. Many hooks are completely digested by chicks, long-term effects of which are entirely unknown. We suggest a number of management approaches for addressing the problem of gear discarding, and guidelines for monitoring schemes elsewhere.

Incidental seabird mortality associated with bycatch during longline commercial fishing is a conservation concern. An initial step to estimating likelihood of seabird bycatch and conceiving conservation strategies is determining amount of overlap between foraging birds and commercial fishing effort, identifying oceanographic features associated with foraging birds, and quantifying dive characteristics. We tracked 24 adult flesh-footed shearwaters (Puffinus carneipes) breeding on Lord Howe Island located east of Australia during incubation and early and late chick-rearing periods from 6 January to 17 April 2005. At-sea foraging distribution of flesh-footed shearwaters was primarily confined within the jurisdictional Australian Fishing Zone. Foraging was strongly associated with sea-surface temperature >24° C. Spatial and temporal overlap of longline fishing with foraging shearwaters varied throughout the breeding season, but was greatest (63% overlap) during early chick-rearing. Mean maximum dista...

The Southern and Eastern Scalefish and Shark Fishery (SESSF) is a complex multi-species fishery, with 34 stock units under quota management, for which a harvest strategy framework was developed in 2005. The framework involves the application of a set of tier-based harvest control rules (HCR) designed to provide a precautionary approach to management. The harvest strategy framework has been applied from 2005 to 2007, resulting in substantial reductions in quotas across the fishery. The experience in implementing the framework, both positive and negative, is described, and general lessons are drawn. Key lessons include the importance of formally testing such strategies using management strategy evaluation, the impact of external management drivers on implementation of the approach, the need to define strategies for setting “bycatch quotas” in multi-species fisheries, and the need for flexibility and pragmatism in the early stages of implementing such an approach.

Hundreds of thousands of seabirds are killed each year as a result of interacting with longline and trawl fishing operations, and the severity of the impact varies regionally. Shy and white-capped albatrosses, Thalassarche cauta and Thalassarche steadi respectively, are phenotypically similar species known to be incidentally killed by fishing operations. The magnitude of this mortality has not previously been assessed across their range. Here we examine recent effort and bycatch rates in fisheries known to incidentally kill these species and qualitatively evaluate the level of impact of each fishery. Results indicate that over 8500 of these albatrosses may be killed annually, although the reliability of this estimate is low due to the paucity of comprehensive observer data in most fisheries. Of the estimated deaths of all seabird species in the fisheries assessed, trawl and longline fisheries killed birds in approximately equal proportions, but when the mortality levels of shy-type albatrosses were examined, trawl fisheries were responsible for 75% of all deaths. Data suggest most of these birds were killed in South African, Namibian and New Zealand demersal trawl fisheries and the South Africa pelagic longline fishery. Because most adult shy albatrosses are comparatively sedentary and rarely found outside Australian waters, it is primarily juvenile shy albatrosses that regularly encounter fishing fleets known to kill large numbers of albatrosses. In contrast, throughout most of their range juvenile and adult white-capped albatrosses are exposed to fisheries that collectively kill many thousands of these albatrosses each year. These data emphasise the urgent need for robust assessments of the impact of bycatch at a species and population level, and the urgent implementation of effective mitigation measures.

The endangered Tristan albatross Diomedea dabbenena is restricted to Gough and Inaccessible Islands. The species is killed as bycatch by longline fisheries in the South Atlantic, but the impact of this mortality is unknown. We satellite tracked 38 breeding Tristan albatrosses and assessed the seasonal and annual at-sea distribution of these birds in relation to reported pelagic longline fishing effort. These birds ranged across the South Atlantic from 50°W to 15°E with most (97%) daytime satellite fixes between latitudes 30°S and 45°S. Considerable fishing effort occurred within the same latitudes. Although there was no correlation between their at-sea distributions, there was a broad overlap between birds and fishing effort. Estimated bycatch rates for Tristan albatross and other Diomedea species in the South Atlantic, and the spatio-temporal overlap between birds and hooks, yield a predicted annual mortality of 471–554 birds, sufficient to cause population decreases of 3.6–4.3% per year. An index of bird × hook interactions (proportional density of birds multiplied by number of hooks by decadal period for each 5° square of longitude and latitude) indicated that 47% of annual interactions occurred in areas around Gough Island, and 11% and 15% of interactions in areas of the west and east Atlantic, respectively. There were also within seasonal differences in the key areas of overlap. The fishing fleets of Taiwan and Japan are likely to be responsible for most interactions based upon the reported magnitude of effort expended in the South Atlantic by these fleets. Ensuring that licensed fishing vessels within the Tristan da Cunha Exclusive Economic Zone (EEZ) operate using best-practise mitigation measures and with fisheries observer programs, could reduce the potential bycatch mortality of breeding Tristan albatrosses in this region by nearly one third. Thorough implementation of international agreements is required in areas of the high seas where most remaining interactions are predicted to occur.

Longline fisheries have expanded throughout the world's oceans since major commercial distant-water pelagic fleets began fishing for tuna and tuna-like species in the early 1950s. Along with the more recent development and expansion of demersal longline fleets for species such as Patagonian toothfish, these vessels are a major source of mortality to several species of seabird. Vessels can set many thousands of baited hooks in a day across many kilometres of water. These waters are often used as foraging areas by wide-ranging seabirds. Attracted by baits and offal, the birds can be caught on the baited hooks and subsequently drown. To provide a greater understanding of the potential impact of the Southern Ocean's longline fleets on seabird populations, this paper describes the trends in longline effort of the major pelagic and demersal fisheries in southern waters. The total reported effort from all longline fleets south of 30°S has been well over 250 million hooks per year since the early 1990s. However the spatial and temporal distribution of this effort has not been constant. While effort from the Japanese pelagic distant-water longline fleet declined through the 1990s, the Taiwanese fleet expanded dramatically. Likewise demersal fishing for toothfish increased markedly during the mid-1990s. These fisheries, along with substantial illegal longline fisheries, may be placing the long-term viability of many Southern Ocean species of seabird in jeopardy.

We consider optimal strategies for harvesting a population that is composed of two local populations. The local populations are connected by the dispersal of juveniles, e.g. larvae, and together form a metapopulation. We model the metapopulation dynamics using coupled difference equations. Dynamic programming is used to determine policies for exploitation that are economically optimal. The metapopulation harvesting theory is applied to a hypothetical fishery and optimal strategies are compared to harvesting strategies that assume the metapopulation is composed either of single unconnected populations or of one well-mixed population. Local populations that have high per capita larval production should be more conservatively harvested than would be predicted using conventional theory. Recognizing the metapopulation structure of a stock and using the appropriate theory can significantly improve economic gains.

Acoustic surveys can provide accurate estimates of biomass at a particular location at a point in time, but provide a negatively biased estimate of the total spawning population unless the proportion of fish that are unavailable to the survey is accounted for. Changes to the ages and maturity stages of fish caught during the spawning season is evidence for turnover of fish during spawning and, along with information on relative abundance, provides a basis for estimating turnover rates. A model is therefore developed that tracks the numbers of males and females by age as they arrive on the spawning grounds, initiate spawning, complete spawning and leave the spawning grounds. This model can be used to determine the proportion of the spawning biomass on the spawning grounds over the spawning season. It is applied to data for blue grenadier, Macruronus novaezelandiae, off western Tasmania, Australia. The results can be used to estimate the average proportion of the population available to an acoustic survey, although this estimate is not likely to be very precise, owing to the high between-year variation in arrival times. However, the model provides a quantitative estimate of turnover rate that was previously not available, and is a rigorous basis for estimating turnover for stock assessment.