The significance of macroalgae to the diets of juvenile fish and ecosystem function in a tropical coral reef lagoon

Little information is available on the contribution of macroalgae to the food web of the Ningaloo lagoon and its importance in the diets of fish associated with it. This information is important for understanding potential trophic flows from macroalgae to juvenile fish and provides the fundamental data for constructing ecosystem models. In my Honours research, I have examined: the significance of macroalgae, its associated epibionts and infauna in the diets of juvenile and subadult fish in the Ningaloo lagoon, focussing on: 1. the significance of macroalgae in the diets of juvenile fish and how this varies between summer (February) and winter (July) (Chapter 3); and 2. the development and use of an Ecopath with Ecosim ecosystem model to assess trophic flows of macroalgae to functional fish groups (Chapter 4). Fish were sampled in macroalgal beds by a variety of techniques (herding into fence nets by SCUBA, hand spear, and rod and line fishing) in February and July, 2015. A total of 181 fish were caught representing 11 species, with six species caught in both months. Stomach contents were identified to the lowest taxonomic resolution possible and the percent volume of items recorded. Multivariate analyses were used to identify guilds (species with similar diets), and to assess differences in diets between February and July. The results showed that: fleshy macroalgae (e.g. Sargassum spp.) were not as important as filamentous algae to the diets of the juveniles of two nominally herbivorous fish species in February, but became more important in July. Macroalgae were not an important component in the diets of juvenile Lethrinidae, Lutjanidae, or Mullidae, though the infauna associated with the macroalgal beds was important in the diets. Analysis of feeding specialisation found that the smaller size classes of fish in February had a narrower trophic width and a more specialised feeding strategy than larger bodied fish of the same species in July. At this time, fish tended to show a generalist feeding strategy and broad niche width, possibly associated with increasing gape size of the larger fish sampled at this time. These studies provided the basis for defining three distinct functional feeding groups for the Ecopath model: herbivores, zoobenthivores, and carnivores (Chapter 4). The Coral Bay Ecopath model was constructed by modifying an Ecopath model for the Ningaloo system and applying it to an area of the macroalgal beds to examine trophic flows from macroalgae to higher trophic levels. The Coral Bay model had 29 functional groups based on the functional fish feeding groups (adults and juveniles of herbivores, zoobenthivores, carnivore, Lethrinus species and Lethrinus nebulosus - 10 groups) and broad dietary categories (13 groups) identified in Chapter 3, a competitor for algal resources (e.g. turtles - 1 group), predators to the fish groups (e.g. reef sharks and dolphins - 2 groups) and extra groups that were included due to having different functional roles (e.g. phytoplankton, squid and octopus - 3 groups). The model was balanced by adjusting biological parameters, with an emphasis on changing those with the fewest data from the region the most. Macroalgae were the dominant primary producers in the system, and comprised more than 70% of the total consumption of trophic level I groups. Ecopath with Ecosim was used to evaluate the effects of three categories of disturbance, (17 scenarios), affecting primary production, fishing effort and simultaneous changes in both primary production and fishing effort. The results from these predicted that changes in the rate of primary production had a much larger effect on the biomass of functional groups within the Ningaloo lagoon than changes to fishing effort. Since this model was developed with a focus on trophic understanding and not fishing, and it was not possible to tune the model with data from recreational fisheries, therefore, the predictions from the scenarios involving fishing effort should be treated with caution. The results from this study show that the macroalgal beds are important in the diets of some fish species and contribute to trophic flows in the Ningaloo lagoon. This adds to the understanding of their function as habitat for different species and highlights the value of including them in conservation planning for the Ningaloo Marine Park

International Workshop on Recreational Fishing Surveys

Recreational fishing surveys have been conducted by the Department of Primary Industries and Regional Development (DPIRD, formerly Department of Fisheries) since 1975 (Tate et al., 2020). Within Western Australia, the first international workshop on recreational fishing surveys was held in January 2010 at the Western Australian Fisheries Marine Research Laboratories in Perth. The workshop aimed to audit existing survey methods and make recommendations for the design of integrated surveys to estimate recreational fishing harvest, catch and effort at statewide and bioregional scales (Wise & Fletcher 2013)

Imputation of missing count data of recreational boat retrievals from remote camera surveys in the Perth Metropolitan region, Western Australia

In Western Australia (WA), remote cameras have been used to monitor boating activity at boat ramps since 2006 to assist in ongoing recreational fishing surveys. These monitoring schemes are useful tools to validate boating activity (defined here as the number of retrievals) and to corroborate estimates of recreational fishing effort obtained from other surveys. This is because remote cameras (also referred to as digital cameras) can provide complete coverage (i.e. 24 hours, 365 days) of boating activities

Integrated survey of boat-based recreational fishing in inner Shark Bay 2018/19

Inner Shark Bay is a popular recreational fishing destination. As recreational fishing occurs in a World Heritage Area and Marine Park, there is a need for ongoing reliable information on catches. Many boat-based recreational fishers in inner Shark Bay target Pink Snapper (Chrysophrys auratus)

Ecological Risk Assessment for the Peel-Harvey Estuarine Fishery

An ecological risk assessment (ERA) of the Peel-Harvey Estuarine Fisheries (Fisheries) was convened by the Department of Primary Industries and Regional Development, Western Australia (WA) on 9 September 2020. ERAs are conducted by the Department as part of its Ecosystem Based Fisheries Management framework and the outputs will inform the updated harvest strategies for these resources, as well as the upcoming Marine Stewardship Council (MSC) re-assessment of the Fisheries. The Fisheries within the scope of this current ERA include the commercial net and crab trap fishery (West Coast Estuarine Managed Fishery: Area 2), and the blue swimmer crab recreational (drop net and scoop net) fishery

Review of recreational fishing surveys in Western Australia

Recreational fishing has been a popular activity in Western Australia for many years, with an estimated 25% of the population participating in this activity in 2017/18. Recreational fishing surveys have been implemented by the Department of Primary Industries and Regional Development (formally Department of Fisheries) since 1976

Framework for Integration of Data from Remotely Operated Cameras into Recreational Fishery Assessments in Western Australia

Remotely operated cameras can be used for cost-efficient monitoring of recreational fishing activities. This report provides an overview of the current usage of cameras in recreational fishery assessments by the Department of Primary Industries and Regional Development. Since 2006, 32 remotely operated cameras have been installed at 26 locations throughout Western Australia and currently 28 cameras are in use

Recreational fishing for Western Rock Lobster: estimates of participation, effort and catch from 2018/19–2020/21. Fisheries Research Report 313

The Western Rock Lobster (WRL) (Panulirus cygnus) is one of the four Rock Lobster (RL) species found in Western Australia. It was the first fishery in the world to obtain Marine Stewardship Council Certification and the first in Western Australia to be managed under a resource allocation process. Catches from the commercial and recreational sectors are required to determine and monitor Total Allowable Catch (TAC), Total Allowable Recreational Catch (TARC) and proportion of Allowable Harvest Level (AHL) achieved. The TARC is set at 5% of the AHL and evaluated in the harvest strategy based on a 5-year average. Since 2018/19, data for the recreational sector have been collected using phone-recall surveys to provide estimates of participation, fishing effort and retained catch (by numbers) from recreational fishers who hold a RL licence. Average weight, obtained from boat ramp surveys, are used to convert estimates of retained catch from licensed fishers by number to weight. Tour Operator Returns (Charter Logbooks) provide a census of the annual participation, effort and retained catch (by numbers) from charter fishers. Random length samples of WRL are provided by tour operators and converted to weight using a length-weight equation which are then used to covert the retained catch from numbers to weight. Participation in the RL recreational fishery (all species) by licensed fishers (RL licence holders aged five years and older) in 2020/21 (1 February 2020–31 January 2021) was 66.8% or 37,469 fishers (95% CI 35,350–39,587). These values were steady from 2018/19–2020/21 (i.e., the 95% CI overlapped between years). The total fishing effort for RL fishing (all species) in 2020/21 was 522,485 days fished (95%CI 491,063–553,907); of which 76.9% or 401,600 (363,338–439,862) was by potting and 23.1% or 120,885 (93,904–147,866) by diving. These values were steady from 2018/19–2020/21. The majority of fishing effort occurred in the Metro-West Coast region (63.5–68.4%). The retained recreational catch of WRL by licensed fishers in 2020/21, based on an overall (i.e., combined across potting and diving) average weight of 587.4 g, was 526 t (95% CI 460–592); of which 79.8% or 420 t (362–478) was harvested by potting and 20.2% or 106 t (68–145) by diving. Total catch (in tonnes) was steady from 2018/19–2020/21. Retained recreational catch of WRL from charter fishing in 2020/21 was 16 t (based on an overall average weight of 494.9 g), an increase from 9 t in 2018/19 (based on an overall average weight of 569.0 g). The majority of the charter catch was taken by potting (88.9–93.7%). The 5-year average recreational catch (for licensed and charter fishing combined) was 427 t in 2018/19, which represents an AHL of 4.6%. The AHL increased to 4.9% in 2019/20 and 2020/21 with a 5-year average recreational catch of 468 t and 498 t, respectively

Recreational fishing for Western Rock Lobster: estimates of participation, effort and catch from 2018/19–2020/21. Fisheries Research Report 313

The Western Rock Lobster (WRL) (Panulirus cygnus) is one of the four Rock Lobster (RL) species found in Western Australia. It was the first fishery in the world to obtain Marine Stewardship Council Certification and the first in Western Australia to be managed under a resource allocation process. Catches from the commercial and recreational sectors are required to determine and monitor Total Allowable Catch (TAC), Total Allowable Recreational Catch (TARC) and proportion of Allowable Harvest Level (AHL) achieved. The TARC is set at 5% of the AHL and evaluated in the harvest strategy based on a 5-year average. Since 2018/19, data for the recreational sector have been collected using phone-recall surveys to provide estimates of participation, fishing effort and retained catch (by numbers) from recreational fishers who hold a RL licence. Average weight, obtained from boat ramp surveys, are used to convert estimates of retained catch from licensed fishers by number to weight. Tour Operator Returns (Charter Logbooks) provide a census of the annual participation, effort and retained catch (by numbers) from charter fishers. Random length samples of WRL are provided by tour operators and converted to weight using a length-weight equation which are then used to covert the retained catch from numbers to weight. Participation in the RL recreational fishery (all species) by licensed fishers (RL licence holders aged five years and older) in 2020/21 (1 February 2020–31 January 2021) was 66.8% or 37,469 fishers (95% CI 35,350–39,587). These values were steady from 2018/19–2020/21 (i.e., the 95% CI overlapped between years). The total fishing effort for RL fishing (all species) in 2020/21 was 522,485 days fished (95%CI 491,063–553,907); of which 76.9% or 401,600 (363,338–439,862) was by potting and 23.1% or 120,885 (93,904–147,866) by diving. These values were steady from 2018/19–2020/21. The majority of fishing effort occurred in the Metro-West Coast region (63.5–68.4%). The retained recreational catch of WRL by licensed fishers in 2020/21, based on an overall (i.e., combined across potting and diving) average weight of 587.4 g, was 526 t (95% CI 460–592); of which 79.8% or 420 t (362–478) was harvested by potting and 20.2% or 106 t (68–145) by diving. Total catch (in tonnes) was steady from 2018/19–2020/21. Retained recreational catch of WRL from charter fishing in 2020/21 was 16 t (based on an overall average weight of 494.9 g), an increase from 9 t in 2018/19 (based on an overall average weight of 569.0 g). The majority of the charter catch was taken by potting (88.9–93.7%). The 5-year average recreational catch (for licensed and charter fishing combined) was 427 t in 2018/19, which represents an AHL of 4.6%. The AHL increased to 4.9% in 2019/20 and 2020/21 with a 5-year average recreational catch of 468 t and 498 t, respectively

Recreational fishing for Western Rock Lobster: estimates of participation, effort and catch from 1986/87 – 2017/18. Fisheries Research Report 299

The Western Rock Lobster (WRL) fishery is one of Australia’s largest single-species recreational and commercial fisheries. The recreational sector has a long history of harvesting this resource, and there is an ongoing need to provide annual estimates of the recreational catch due to the formal resource sharing policy adopted in 2004. Mailrecall surveys, supplemented with occasional phone-recall surveys, provide costeffective monitoring, since WRL is a single-species, licensed recreational fishery operating across large spatial and temporal scales. This report presents estimates of participation, fishing effort and retained catch from annual mail-recall surveys of randomly selected licensed Rock Lobster (RL) recreational fishers from 1986/87 to 2017/18 and provides comparisons of estimates with phone recall surveys conducted in 2001/02 and from 2015/16 to 2017/18. Participation rates were relatively stable from 1986/87–2004/05 with around 75% of licence holders fishing. Participation rates then began to decline to a low of 52% in 2011/12, before increasing to 64% by 2017/18. The total fishing effort (potting and diving combined; all RL species) increased from 0.41 million fisher days (in 1986/87) to 0.94 million (in 2017/18); an increase of 127%, over the 32 years. Total effort was low and relatively steady, 0.34–0.43 million fisher days per year during 1986/87–1990/91, then increased to 0.59 million days in 1992/93, followed by several years of higher effort occurring in 1998/99 (0.85 million days) and 2002/03 (0.92 million days). Total effort then declined to 0.41 million days in 2011/12 but has since increased to peak at 0.94 million days in 2017/18. Effort by potting was 75–90% of the total effort, compared to 10–25% by diving across all years. The estimated retained catch increased from 96 tonnes (CI 79–112) in 1986/87 to 480 tonnes (390–570) in 2017/18; an increase of 402% over the 32-years. Retained catch followed a similar trend to effort with significant peaks in 1999/00–2004/05 and in 2014/15–2017/18 but varied more from season to season, depending on factors such as lobster recruitment and management changes. Potting harvested 70–85% of the lobsters, compared to 15–30% by diving across all years. The trends in participation, fishing effort and retained catch vary over the 32-time period and have been influenced by various societal, biological, and management factors, including changing abundance and recruitment of RL stocks and management regulations (i.e. season length, size and bag limits). Phone-recall surveys were introduced as an alternative method of estimating recreational catch, due to declining survey responses for the mail-recall surveys. Phone-recall surveys were less biased from survey non-response and produced lower estimates of participation, fishing effort and retained catch than the mail survey. The lower estimates in the phone-recall survey were predominantly from pot fisher responses, whereas estimates for dive fishing were generally similar between survey methods