Reproductive parameters of rhinobatid and urolophid batoids taken as by-catch in the Queensland (Australia) east coast otter-trawl fishery

Reproductive variables are provided for batoids regularly taken as by-catch in the east coast otter-trawl fishery on the inner-mid continental shelf off the south-east and central coasts of Queensland, Australia. Total length at maturity (LT50 and 95% c.i.) for the eastern shovelnose ray Aptychotrema rostrata was 639·5 mm (617·6–663·4 mm) for females and 597·3 mm (551·4–648·6 mm) for males. Litter size (n = 9) ranged from nine to 20 (mean ± s.e. = 15·1 ± 1·2). This species exhibited a positive litter size–maternal size relationship. Disc width at maturity (WD50 and 95% c.i.) for the common stingaree Trygonoptera testacea was 162·7 mm (155·8–168·5 mm) for females and 145·9 mm (140·2–150·2 mm) for males. Gravid T. testacea (n = 6) each carried a single egg in the one functional (left) uterus. Disc width at maturity (WD50 and 95% c.i.) for the Kapala stingaree Urolophus kapalensis was 153·7 mm (145·1–160·4 mm) for females and 155·2 mm (149·1–159·1 mm) for males. Gravid U. kapalensis (n = 16) each carried a single egg or embryo in the one functional (left) uterus. A single female yellowback stingaree Urolophus sufflavus carried an embryo in each uterus. A global review of the litter sizes of shovelnose rays (Rhinobatidae) and stingarees (Urolophidae) is provided.

Stout Whiting Fishery Summary : Commercial Quota Setting for 2017

This fishery assessment report describes the commercial stout whiting fishery operation along Australia’s east coast between Sandy Cape and the Queensland-New South Wales border. The fishery is identified by a T4 symbol. This study follows methods applied in (O'Neill & Leigh, 2016a) and extends the results of that study by using the latest data available up to end of March 2016. The fishery statistics reported herein are for fishing years 1991 to 2016. This study analysed stout whiting catch rates from both Queensland and New South Wales (NSW) for all vessels, areas and fishing gears. The 2016 catch rate index from Queensland and NSW waters was 0.86. This means that the 2016 catch rate index was 86% of the mean standardised catch rate. Results showed that there was a stable trend in catch rates from 2012 to 2016, as in the previous study (O'Neill & Leigh, 2016a), with the 2015 and 2014 catch rates 85% of the mean catch rate. The fish-length frequency and age-length-otolith data were translated using two models which showed: • Where patterns of fish age-abundance were estimated from the fish-length frequency and age-length data, there were slightly decreased estimated measures of fish survival at 38% for 2014, compared to fish survival estimates in 2013 at 40%. The 2014 and 2015 estimated age structure was dominated by 1+ and 2+ old fished, with a slightly higher frequency of age 2 - 3 fish for 2015. • Where only the age-length data were used, estimates showed that from 2011 to 2014 the survival index increased. The estimated survival index increased from 35% in 2013 to 64% in 2014, indicating stronger survival of fish as they recruited and aged. Together the stout whiting catch rate and survival indicators showed the recent fishery harvests were sustainable. Since 1997, T4 management (Stout Whiting Fishery) is centred on annual assessments of total allowable commercial catch (TACC). The TACC is assessed before the start of each fishing year using statistical assessment methodologies, namely evaluation of trends in fish catch rates and catch-at-age frequencies measured against management reference points. The TACC has been under-caught in many years. For setting the 2017 T4 stout whiting TACC, the calculations covered a range of settings to account for the variance in the data and provide options for quota change. The overall (averaged) results suggested: • The procedure where the quota was adjusted based on previous TACC setting in year 2016 gave a recommended TACC for 2017 of between 1100 and 1130 t. • The procedure that focussed directly on optimising the average harvest to match target reference points gave a recommended TACC for 2017 of between 860 and 890 t. Use of these estimates to set TACC will depend on management and industry aims for the fishery.

Mixture of time-dependent growth models with an application to blue swimmer crab length-frequency data

Understanding how aquatic species grow is fundamental in fisheries because stock assessment often relies on growth dependent statistical models. Length-frequency-based methods become important when more applicable data for growth model estimation are either not available or very expensive. In this article, we develop a new framework for growth estimation from length-frequency data using a generalized von Bertalanffy growth model (VBGM) framework that allows for time-dependent covariates to be incorporated. A finite mixture of normal distributions is used to model the length-frequency cohorts of each month with the means constrained to follow a VBGM. The variances of the finite mixture components are constrained to be a function of mean length, reducing the number of parameters and allowing for an estimate of the variance at any length. To optimize the likelihood, we use a minorization–maximization (MM) algorithm with a Nelder–Mead sub-step. This work was motivated by the decline in catches of the blue swimmer crab (BSC) (Portunus armatus) off the east coast of Queensland, Australia. We test the method with a simulation study and then apply it to the BSC fishery data.

Rising temperatures increased recruitment of brown tiger prawn (Penaeus esculentus) in Moreton Bay (Australia)

Abiotic factors are fundamental drivers of the dynamics of wild marine fish populations. Identifying and quantifying their influence on species targeted by the fishing industry is difficult and very important for managing fisheries in a changing climate. Using multiple regression, we investigated the influence of both temperature and rainfall on the variability of recruitment of a tropical species, the brown tiger prawn (Penaeus esculentus), in Moreton Bay which is located near the southern limit of its distribution on the east coast of Australia. A step-wise selection between environmental variables identified that variations in recruitment from 1990 to 2014 were best explained by a combination of temperature and spawning stock biomass. Temperature explains 35% of recruitment variability and spawning stock biomass 33%. This analysis suggests that increasing temperatures have increased recruitment of brown tiger prawn in Moreton Bay.