8.2.1 Commercial Catch and Effort
All fishers operating in the WCEMF and SBBSMNF are required to fill out and submit monthly statutory catch and effort statistics (CAES). These data have been used to provide the basis for ongoing stock assessment and are critical to the development of stock performance indices and harvest strategy evaluation.
Under the Fish Resources Management Act 1994 (FRMA), licensees involved in fishing operations and/or the master of every licensed fishing boat must submit an accurate and complete monthly catch and effort return on forms approved by the Department. These returns record the monthly catch totals (to the nearest kilogram) for each retained species, monthly effort (total days fished), estimates of daily effort (e.g., average hours fished per day, average length of net deployed per day) and spatial information by block (60 x 60 nm) fished, along with bycatch and threatened
species interactions, per method used. These data are collected and collated by DPIRD and stored in a Catch and Effort Statistics (CAES) database.
It should be noted that catch records for whiting species in CAES must be interpreted with caution as commercial fishers often do not report catches at the species level on their returns.
Reporting of effort by commercial fishers in their statutory CAES returns is also problematic as nearshore and estuarine commercial fisheries are multi-species and multi-gear. Catch and effort is reported as monthly summaries. Usually, the effort expended towards a particular species cannot be precisely quantified due to the monthly aggregation of data, although it may be possible to obtain a reasonable estimate in situations where the species is known to be the main target and makes up the majority of the catch.
In addition to ‘number of days fished’, fishers are required to report the ‘mesh size’,
‘net length’, ‘hours fished per day’ ‘and ‘number of shots per day’ for each net type on their monthly returns. However, the single value given for the month does not allow for daily variations (which presumably occur) in each variable and is therefore potentially unreliable.
Also, ‘hours fished’ is open to interpretation by individual fishers. It could include searching, traveling and/or soak time depending on how fishers choose to quantify their effort. Searching/spotting is an integral part of beach seine and haul net fishing, but it can be difficult to quantify.
For the above reasons, it is generally not possible to detect fine-scale variations in total effort in commercial netting fisheries. Pre-1975, the number of licenced vessels in the fishery is often the only available measure of effort. Post-1975, ‘method day’
(the no. of days that a particular gear type was deployed within a block within a month, ‘Bday’ in CAES) is usually the most reliable measure of effort.
8.2.2 Recreational / Charter Catch and Effort
Since 2011, a biennial state-wide recreational survey has been undertaken to collect information on private (non-charter) recreational boat-based catch and effort in WA (Ryan et al. 2013, 2015, 2017, 2019). This survey uses three complementary components, off-site phone diary surveys, on-site boat ramp surveys and remote camera monitoring, to collect information on catch, effort, location, and other demographic information, every two to three years. The latest 2017/18 survey also collected some information on shore-based recreational fishing by surveyed fishers.
Since 2001, it has been a statutory requirement for boat-based charter fishing operators to submit monthly returns detailing catches and effort.
A voluntary recreational daily logbook scheme (Research Angler Program, RAP) commenced in 2004/05. Contributing fishers record information on their catch (no. of fish), effort (hours and fishing method/gear type and number used) and catch
composition (size, sex, discard information), along with generalised spatial data (Figure 8.1). The majority of participants are in the WCB, including shore- and boat- based recreational fishers. The RAP provides some data not currently available from other sources, especially for shore-based fishing.
Figure 8.1. Voluntary research log sheet completed by recreational fishers as part of the Recreational Angler Program (RAP).
8.2.3 Fishery-Dependent Monitoring
Information about the age and length composition of fishery landings is collected periodically for a number of indicator species in the south-west estuarine and nearshore finfish resource to inform weight-of-evidence assessments of these stocks. The age of sampled fish is estimated by counting the number of opaque zones in otoliths, following documented quality control protocols for each species.
The annual periodicity of opaque zones has been validated for sea mullet (Smith and Deguara 2003) and yellowfin whiting (Hyndes and Potter 1997, Coulson et al. 2005).
Fishery-dependent monitoring of sea mullet for age and length composition in fishery landings were most recently undertaken in the WCB in 2016/17 and 2017/18, and in the GCB (Shark Bay) in 2018 and 2019. Fishery-dependent monitoring of yellowfin whiting for age and length composition in fishery landings was most recently
undertaken in the WCB (Peel-Harvey, Bunbury, Hardy Inlet, Wonnerup and Binnigup) between 2015 and 2017, and in 2014 in the GCB (Shark Bay).
Samples of commercially caught sea mullet have been collected from the GCB, WCB and SCB regions during 2020 and 2021 for genetic analysis aimed at
determining the stock connectivity of this species along the WA coast. Samples of yellowfin whiting were also collected, along with samples collected opportunistically
during 2020/21 recruitment index surveys in the WCB (Koombana Bay, Warnbro Sound and Mangles Bay), for a South Australian research project aiming to establish the population structure and connectivity of yellowfin whiting on evolutionary scales across the entire southwest Australian range.
8.2.4 Fishery-Independent Monitoring
Fishery-independent seine net surveys have been conducted by DoF at multiple beaches in the WCB and SCB since 1995 (Gaughan et al. 2006) to monitor annual recruitment trends and provide biological information (e.g., growth, reproduction, recruitment, distribution) that could support formal stock assessments for key indicator species (e.g., whiting spp., herring, salmon, mullet).
Between 1995 and June 2002, sampling occurred on a monthly basis at six sites:
Poison Creek (170 km east of Esperance), Emu Beach (Albany), Koombana Bay (Bunbury), Warnbro Sound, Mangles Bay (Cockburn Sound) and Pinnaroo Point (Perth). Sampling was discontinued from July 2002 due to budgetary constraints, before recommencing in September 2005 with sampling refined to 8 months of the year (September through to April). A site in the Leschenault Estuary was included in 2006, while sampling at the Emu Beach site was discontinued in 2010 due to
changing beach conditions prohibiting sampling.
The seine netting program was again discontinued in May 2016, before recommencing in September 2020.
8.2.5 Environmental Monitoring
Databases with environmental variables (e.g., water temperature, wind, and sea level) are continuously updated and extended as new data becomes available from collections by the Department, internet sources and from other agencies (see Caputi et al. 2015). The environmental variables from these databases have been used in analyses of correlations with biological parameters of species and allow for the examination of long-term trends.
8.2.6 Other Information
Biological parameters and other information used in assessments are available from numerous fishery-independent studies in WA conducted by universities.