Dynamic catch trends in the history of recreational spearfishing in Australia

Assessing changes in threatened black rockcod Epinephelus daemelii abundance and length over the past 15 years in New South Wales, Australia

Ideally, protection of a threatened fish will lead to their recovery in abundance, distribution, and size structure within the population, to a point where they are no longer considered threatened. Monitoring abundance and size is crucial to evaluate this, although low numbers associated with being threatened can strongly constrain the methods used. To assess if population recovery is occurring for the black rockcod Epinephelus daemelii, a large subtropical grouper endemic to shallow reefs in the southwest Pacific, surveys were undertaken across northern New South Wales and Lord Howe Island using roving diver timed counts and diver stereo-video measurements to assess relative abundance and length. Surveys in 2023 were compared with initial baseline data captured in 2009-2011 using the same methods. Relative abundance of E. daemelii at long-term monitoring sites has remained relatively constant or declined since 2010 rather than increasing. Comparisons between 84 broadscale sites in 2009-2011 versus 2023 (117 vs. 69 observed E. daemelii) indicate a recent decline in abundance. Although protected from fishing and spearfishing for over 40 years, the relative abundance of E. daemelii does not appear to be increasing over the past 15 years since monitoring commenced. This is a concerning trend that does not indicate recovery, although an increase in the proportion of mature females in the population from 2010 to 2023 is positive. As E. daemelii is slow growing, long lived, late to mature and still susceptible to incidental capture mortality, more active management may be needed to help assist with the slow recovery of this threatened species.

John TL, Schmid S, Pirkle CM. Spearfishing and public health promotion: A cross-sectional analysis of the Hawai'i Behavioral Risk Factor Surveillance System Survey

Spearfishing, a culturally relevant practice in many locations globally, may foster physical activity and enhance well-being by promoting social cohesion, food security, and nature connectedness, but is understudied in public health promotion and surveillance. This study measured the population-level prevalence of lifetime spearfishing engagement in Hawai'i and identified associated factors for public health promotion. The Hawaiian Islands present an ideal setting for such activities due to its central Pacific location and a diverse population with cultural ties to spearfishing. In 2019 and 2020, lifetime spearfishing engagement was added to the Hawai'i Behavioral Risk Factor Surveillance System (N = 12,737). Prevalence ratios (PR) and 95% confidence intervals (95%CI) were estimated for spearfishing "sometimes," "often," or "very often" during one's lifetime, considering sociodemographic, health behavior, and health status variables. A quarter of respondents statewide reported engagement, with higher rates amongst men (41%), Native Hawaiians (43%), other Pacific Islanders (36%), American Indian or Alaskan Native (32%), and rural island residents of Lāna'i (51%) and Moloka'i (43%). All age groups reported similar lifetime engagement. After statistical adjustment, those with a high school diploma or less were significantly more likely to have engaged in spearfishing than those with higher education. Spearfishing engagement was also associated with a higher likelihood of meeting physical activity guidelines (PR 1.45 95%CI 1.29-1.63). There is widespread lifelong engagement in spearfishing in Hawai'i, especially among Indigenous and rural populations. Supporting culturally relevant activities, such as spearfishing, is a strength-based approach to health promotion with global relevance, including encouraging physical activity.

Quantifying Catch Rates, Shark Abundance and Depredation Rate at a Spearfishing Competition on the Great Barrier Reef, Australia

We developed and applied a method to quantify spearfisher effort and catch, shark interactions and shark depredation in a boat-based recreational spearfishing competition in the Great Barrier Reef Marine Park in Queensland. Survey questions were designed to collect targeted quantitative data whilst minimising the survey burden of spearfishers. We provide the first known scientific study of shark depredation during a recreational spearfishing competition and the first scientific study of shark depredation in the Great Barrier Reef region. During the two-day spearfishing competition, nine vessels with a total of 33 spearfishers reported a catch of 144 fish for 115 h of effort (1.25 fish per hour). A subset of the catch comprised nine eligible species under competition rules, of which 47 pelagic fish were weighed. The largest fish captured was a 34.4 kg Sailfish (Istiophorus platypterus). The most common species captured and weighed was Spanish Mackerel (Scomberomorus commerson). The total weight of eligible fish was 332 kg and the average weight of each fish was 7.1 kg. During the two-day event, spearfishers functioned as citizen scientists and counted 358 sharks (115 h effort), averaging 3.11 sharks per hour. Grey Reef Sharks (Carcharhinus amblyrhynchos) comprised 64% of sightings. Nine speared fish were fully depredated by sharks as spearfishers attempted to retrieve their catch, which equates to a depredation rate of 5.9%. The depredated fish included four pelagic fish and five reef fish. The shark species responsible were Grey Reef Shark (C. amblyrhynchos) (66%), Bull Shark (Carcharhinus leucas) (11%), Whitetip Reef Shark (Triaenodon obesus) (11%) and Great Hammerhead (Sphyrna mokarran) (11%). There were spatial differences in fish catch, shark sightings and rates of depredation. We developed a report card that compared average catch of fish, sightings of sharks per hour and depredation rate by survey area, which assists recreational fishers and marine park managers to assess spatio-temporal changes. The participating spearfishers can be regarded as experienced (average 18 days a year for average 13.4 years). Sixty percent of interviewees perceived that shark numbers have increased in the past 10 years, 33% indicated no change and 7% indicated shark numbers had decreased. Total fuel use of all vessels was 2819 L and was equivalent to 6.48 tons of greenhouse gas emissions for the competition.

Preferences and perceptions of the recreational spearfishery of the Great Barrier Reef

Recreational fishing practices can have significant impacts on marine ecosystems but their catch dynamics are often difficult to quantify, particularly for spearfishing. On coral reefs, the impacts of recreational spearfishing are often considered to be negligible compared to other practices, but the highly selective method adopted by spearfishers can result in locally distinct ecological consequences. Here we investigated the spatial patterns and catch composition of recreational spearfishers on the Great Barrier Reef using an online survey (n = 141 participants) targeted at spearfishers active along the coastline of Queensland. Observations from within the Queensland spearfishing community were also used to explore perceived changes in catches of three functionally distinct spearing targets. Preferred reef regions (coastal, inshore, offshore) differed among spearfishers from Bundaberg (south) to Cooktown (north). The piscivorous coral trout, Plectropomus leopardus, was suggested to be the preferred target comprising 34% (±1.5 SE) of spearfishers' reported catch composition. Spearfishers also noted a variety of changes in their catch composition over time, particularly regarding parrotfishes (decreased landings) and tuskfishes (increased landings). How this relates to the relative abundance and population biology of these taxa on the Great Barrier Reef requires attention. Spearfishers can provide important information regarding the status of their fishery through direct observations, which can inform legislation when acknowledged.

Implementing Sustainably Managed Fisheries Using Ecological Risk Assessment and Bowtie Analysis

Determining the effectiveness of a management system to enable fisheries to harvest sustainably is a key challenge. To fully assess the likelihood that a fishery management system will not achieve its sustainability objectives, the assessment needs to include the whole pathway that leads to the consequences for management objectives. A crucial aspect of the pathway is the inclusion of management controls. Effectiveness of these management controls determines whether the effects of human pressures on ecological components and their impacts are reduced to a level that will not impede management achieving their objectives. Ecological risk assessments do not provide sufficient information to make decisions about what to change specifically in a management system to ensure a fishery is sustainably managed. Bowtie analysis (BTA) is a method that logically connects the relationships between management objectives, management controls, threats, potential impacts of threats on the fishery resource and the consequences of those impacts on achieving the management objectives. The combination of bowtie analysis and ecological risk assessment enables managers, scientists and stakeholders to evaluate different management controls and research options in response to risk factors and track the effectiveness of the management system. We applied a three-step method of bowtie analysis stage 1, quantitative ecological risk assessment and bowtie analysis stage 2 to evaluate fisheries management and science. We demonstrate these steps using a case study of a commercially fished species in New South Wales, Australia.

Social interactions among grazing reef fish drive material flux in a coral reef ecosystem

In human financial and social systems, exchanges of information among individuals cause speculative bubbles, behavioral cascades, and other correlated actions that profoundly influence system-level function. Exchanges of information are also widespread in ecological systems, but their effects on ecosystem-level processes are largely unknown. Herbivory is a critical ecological process in coral reefs, where diverse assemblages of fish maintain reef health by controlling the abundance of algae. Here, we show that social interactions have a major effect on fish grazing rates in a reef ecosystem. We combined a system for observing and manipulating large foraging areas in a coral reef with a class of dynamical decision-making models to reveal that reef fish use information about the density and actions of nearby fish to decide when to feed on algae and when to flee foraging areas. This "behavioral coupling" causes bursts of feeding activity that account for up to 68% of the fish community's consumption of algae. Moreover, correlations in fish behavior induce a feedback, whereby each fish spends less time feeding when fewer fish are present, suggesting that reducing fish stocks may not only reduce total algal consumption but could decrease the amount of algae each remaining fish consumes. Our results demonstrate that social interactions among consumers can have a dominant effect on the flux of energy and materials through ecosystems, and our methodology paves the way for rigorous in situ measurements of the behavioral rules that underlie ecological rates in other natural systems.