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Several odontocete species depredate catch and bait from fishing gear, resulting in their bycatch and causing substantial economic costs. There are no known mitigation methods for odontocete depredation in pelagic longline fisheries that are effective, do not harm odontocetes and are commercially viable. Understanding odontocetes' depredation strategies can contribute to mitigating this human-wildlife conflict. Using observer data from the Hawaii-based tuna longline fishery, this study summarized teleost and elasmobranch species-specific mean posterior odontocete depredation rates using a simple Bayesian binomial likelihood estimator with a Bayes-Laplace prior. Depredation rates of species with sufficient sample sizes ranged from a high of 1.2% (1.1 to 1.3 95% highest posterior density interval or HDI) for shortbill spearfish to a low of 0.002% (0.001 to 0.003 95% HDI) for blue shark. Depredation of catch is a rare event in this fishery, occurring in about 6% of sets. When depredation did occur, most frequently odontocetes depredated a small proportion of the catch, however, there was large variability in depredation rates between teleost species. For example, bigeye tuna was two times more likely to be depredated than yellowfin tuna (odds ratio = 2.03, 95% CI: 1.8–2.3, P<0.0001). For sets with depredation, 10% and 2% of sets had depredation of over half of the captured bigeye tuna and combined teleosts, respectively. All elasmobranch species had relatively low depredation rates, where only 7 of almost 0.5M captured elasmobranchs were depredated. Odontocetes selectively depredate a subset of the teleost species captured within sets, possibly based on net energy value, chemical, visual, acoustic and textural characteristics and body size, but not median length, which was found to be unrelated to depredation rate (Pearson's r = 0.14, 95% CI: -0.26 to 0.50, p = 0.49). Study findings provide evidence to support the identification and innovation of effective and commercially viable methods to mitigate odontocete depredation and bycatch. [ABSTRACT FROM AUTHOR]

ABSTRACT Declines in absolute abundance and altered size distributions from size-selective removals of market species of pelagic apex predators in tuna fisheries alters evolutionary characteristics of populations and ecosystem processes and stability. Pelagic fishing at seamounts, where hyperstability of pelagic predators may occur, can exacerbate declining abundance and have high bycatch of species groups that are highly vulnerable to overexploitation., Generalized additive mixed Poisson regression models (GAMMs) were fitted to Hawaii longline tuna fishery observer data to determine temporal trends in standardized catch rates, an index for local, relative abundance. Temporal trends in expectile length distributions were determined through geoadditive expectile GAMMs., Significant declining trends in relative abundance in this fishery were observed for tunas, sharks and billfish. A decline in seabird standardized catch rate occurred concurrently with the uptake of seabird bycatch mitigation technology. Changed spatial distribution of fishing effort and increased use of wider circle hooks likely contributed to a declining sea turtle standardized catch rate., Tuna and billfish mean lengths significantly increased over the time series due to entire distributions of length classes having shifted towards larger fish. Larger tunas comprised a larger proportion of the catch due to fewer small tunas being caught, and to a lesser extent because mean lengths of larger size classes increased. Conversely, billfish largest length classes experienced the largest increases in average lengths. Changes in spatial and seasonal distributions of fishing effort, increased use of wider circle hooks, and possibly increasing purse seine selective removals of juvenile tunas, may have contributed to increased selectivity for larger fish., Significant differences in standardized catch rates and length distributions at a shallow seamount vs. the open ocean confirms the aggregating effect of seamounts on pelagic predators, including juvenile market species of pelagic fish and species groups relatively vulnerable to overexploitation., Wider circle hooks significantly improved valuable tuna standardized catch rates, but also increased unwanted shark and reduced valuable billfish standardized catch rates., Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

We investigated cause-specific temporal and spatial trends in sea turtle strandings in the Hawaiian Archipelago. Five species of sea turtle were recorded in 3,861 strandings over a 22-year period (1982–2003). Green turtles comprised 97% of these strandings with size and gender composition reflecting the demographic structure of the resident green turtle population and relative green turtle abundance in Hawaiian waters. The cause of strandings was determined by necropsy based on a complete gross external and internal examination. Totally 75% of the 3,732 green turtle strandings were from Oahu where strandings occur year-round. The most common known cause of the green turtle strandings was the tumour-forming disease, fibropapillomatosis (28%) followed by hook-and-line fishing gear-induced trauma (7%), gillnet fishing gear-induced trauma (5%), boat strike (2.5%), and shark attack (2.7%). Miscellaneous causes comprised 5.4% of strandings whereas 49% of green turtle strandings could not be attributed to any known cause. Green turtle strandings attributable to boat strike were more likely from Kauai and Oahu while fibropapilloma strandings were more likely from Oahu and Maui. Hook-and-line gear strandings were more likely from Oahu due to higher per capita inshore fishing effort. The specific mortality rate (conditional probability) for fibropapillomatosis was 88%, 69% for gillnet gear and 52% for hook-and-line gear. The probability of a dead green turtle stranding increased from 1982 but levelled off by the mid-1990s. The declining mortality risk was because the prevalence and severity of fibropapillomatosis has decreased recently and so has the mortality risk attributable to gillnet gear. Despite exposure to disease and inshore fishing gears, the Hawaiian green turtle stock continues to recover following protection since the late 1970s. Nevertheless, measures to reduce incidental capture of sea turtles in coastal Hawaiian fisheries would be prudent, especially since strandings attributable to hook-and-line fishing gear have increased steadily since 1982. [ABSTRACT FROM AUTHOR]

Aim To critically review the status of the green sea turtle ( Chelonia mydas) using the best available scientific studies as there is a prevailing view that this species is globally endangered and its marine ecosystem functions compromised. Location Ogasawara (Japan), Hawaii (USA), Great Barrier Reef (Australia), Florida (USA), Tortuguero (Costa Rica). Methods We compiled seasonal nesting activity data from all reliable continuous long-term studies (> 25 years), which comprised data series for six of the world's major green turtle rookeries. We estimated the underlying time-specific trend in these six rookery-specific nester or nest abundance series using a generalized smoothing spline regression approach. Results Estimated rates of nesting population increase ranged from c. 4–14% per annum over the past two to three decades. These rates varied considerably among the rookeries, reflecting the level of historical exploitation. Similar increases in nesting population were also evident for many other green turtle stocks that have been monitored for shorter durations than the long-term studies presented here. Main conclusions We show that six of the major green turtle nesting populations in the world have been increasing over the past two to three decades following protection from human hazards such as exploitation of eggs and turtles. This population recovery or rebound capacity is encouraging and suggests that the green turtle is not on the brink of global extinction even though some stocks have been seriously depleted and are still below historical abundance levels. This demonstrates that relatively simple conservation strategies can have a profound effect on the recovery of once-depleted green turtle stocks and presumably the restoration of their ecological function as major marine consumers. [ABSTRACT FROM AUTHOR]

The Hawaiian green sea turtle genetic stock is endemic to the Hawaiian Archipelago. This stock was depleted over the past century mainly due to over-exploitation that ceased during the 1970s following protection under the US Endangered Species Act. Nesting trends suggest the stock has been recovering but no formal stock assessment has been undertaken. So, we used a Bayesian state-space surplus-production model to describe Hawaiian green turtle population dynamics given limited data and uncertainty about sea turtle demography. Data series comprised commercial landings of green turtles reported from the Archipelago (1944–1973) and nester abundance recorded at the primary rookery on East Island, French Frigate Shoals (1973–2004). The model incorporated process and observation error and was fitted using Markov chain Monte Carlo simulation with a mix of informative and non-informative priors. We estimated that the Hawaiian green turtle stock was ca. 20% of pre-exploitation biomass when monitoring and protection began in the 1970s. The stock is estimated to be now ca. 83% of pre-exploitation biomass with an intrinsic growth rate ca. 5.4% pa (95% Bayesian credible interval: 3.1–8.9%). Rebound or recovery potential (also exploitation rate at MSP) of this stock was estimated to be 3.4% (1.6–6.2%), which is consistent with estimates for other long-lived late-maturing marine species. So, this once-seriously-depleted green turtle stock is well on the way to recovery and a limited harvest might now be demographically feasible. These findings are relevant for supporting informed public policy debate on the restoration of indigenous hunting rights in the Archipelago. Parameter estimates and model structure from the Bayesian surplus-production model were incorporated in an interactive easy-to-use stochastic simulation model to help support policy analysts in stock recovery planning and to explore sustainable harvest potential. [Copyright &y& Elsevier]

The green sea turtle is one of the long-lived species that comprise the charismatic marine megafauna. The green turtle has a long history of human exploitation with some stocks extinct. Here we report on a 30-year study of the nesting abundance of the green turtle stock endemic to the Hawaiian Archipelago. We show that there has been a substantial long-term increase in abundance of this once seriously depleted stock following cessation of harvesting since the 1970s. This population increase has occurred in a far shorter period of time than previously thought possible. There was also a distinct 3–4 year periodicity in annual nesting abundance that might be a function of regional environmental stochasticity that synchronises breeding behaviour throughout the Archipelago. This is one of the few reliable long-term population abundance time series for a large long-lived marine species, which are needed for gaining insights into the recovery process of long-lived marine species and long-term ecological processes. [Copyright &y& Elsevier]

Bycatch in longline fisheries threatens the viability of some seabird populations. The Hawaii longline swordfish fishery reduced seabird captures by an order of magnitude primarily through mitigating bycatch during setting. Now, 75% of captures occur during hauling. We fit observer data to a generalized additive regression model with mixed effects to determine the significance of the effect of various factors on the standardized seabird haul catch rate. Density of albatrosses attending vessels during hauling, leader length and year had largest model effects. The standardized haul catch rate significantly increased with increased albatross density during hauling. The standardized catch rate was significantly higher the longer the leader: shorter leaders place weighted swivels closer to hooks, reducing the likelihood of baited hooks becoming available to surface-scavenging albatrosses. There was a significant linear increasing temporal trend in the standardized catch rate, possibly partly due to an observed increasing temporal trend in the local abundance of albatrosses attending vessels during hauling. Swivel weight, Beaufort scale and season were also significant but smaller model effects. Most (81%) haul captures were on branchlines actively being retrieved. Future haul mitigation research should therefore focus on reducing bird access to hooks as crew coil branchlines, including methods identified here of shorter leaders and heavier swivels, and other potentially effective methods, including faster branchline coiling and shielding the area where hooks becomes accessible. The proportion of Laysan albatross (Phoebastria immutabilis) captures that occurred during hauling was significantly, 1.6 times, higher than for black-footed albatrosses (P. nigripes), perhaps due to differences in the time of day of foraging and in daytime scavenging competitiveness; mitigating haul bycatch would therefore be a larger benefit to Laysans. Locally, findings identify opportunities to nearly eliminate seabird bycatch. Globally, findings fill a gap in knowledge of methods to mitigate seabird bycatch during pelagic longline hauling.

Estimates of chronic disease prevalence are needed to improve our understanding of marine disease epizootiology, which is poorly known for marine megafauna such as marine turtles. An emerging worldwide threat to green sea turtles (Chelonia mydas) is fibropapillomatosis (FP), which is a pandemic tumor-forming disease associated with herpes-viruses. We report on a 26-yr FP epidemic in the Hawaiian Archipelago and show that apparent disease prevalence in the world's main endemic hot spot increased rapidly following a late 1980s outbreak, peaked during the mid-1990s, and then declined steadily ever since. While this disease is a major cause of sea turtle stranding in Hawaiian waters and can be fatal, we also show that long-term tumor regression can occur even for turtles with advanced FP. The endemic Hawaiian green turtle stock was severely depleted by overexploitation prior to protection under the US Endangered Species Act in 1978. This stock has increased significantly ever since, despite exposure to a major chronic disease epidemic that is currently declining.