Environmental indices for spanner crab (Ranina ranina) catch rates depend on regional oceanographic features. (15th November 2019)

• Record Type: Journal Article
• Authors: Spencer, David M.; Doubell, Mark J.; Brown, Ian W.; Redondo Rodriguez, Ana; Lee, Shing Y.; Lemckert, Charles J.
• Is Part Of: Estuarine, coastal and shelf science. Volume 228(2019)
• Publication Date: 2019-11-15
• Subjects: Estuarine oceanography -- Periodicals; Coasts -- Periodicals; Estuarine biology -- Periodicals; Seashore biology -- Periodicals; Coasts; Estuarine biology; Estuarine oceanography; Seashore biology; Periodicals; 551.461805
• DOI: 10.1016/j.ecss.2019.106361
• Languages: English
• ISSNs: 0272-7714

Abstract

Abstract: In the Australian spanner crab ( Ranina ranina ) fishery, management and industry are looking for improvements to the existing indicators of stock abundance. Prior research linked several oceanographic indices to the catchability of spanner crabs; however, it was unclear whether nearshore (e.g. river-runoff) or region-specific oceanographic features (e.g. eddies and the East Australian Current) are responsible for these effects on catch rates. Using satellite remote sensing and fishery-independent survey data, we analysed the influence of oceanographic and environmental indices on spanner crab catch rates in southern Queensland. Outputs from Generalised Additive Models (GAM) show that catch rates exhibit a large amount of variability between different regions of the fishery, with highest catch rates at fishing grounds within 40 km from the shelf break. Offshore oceanic waters, transported into various regions by different oceanographic processes, were linked to an increase in catch rates. Lower concentrations of surface chlorophyll a were also correlated with higher catch rates, but only in survey regions exposed to the effects of the Fraser Gyre and at the mouth of bays. Overall, results highlighted that the effects of environmental indices on catch rates were not homogeneous across the fishery. Rather, relationships were linked to region-specific (<100 km), highly dynamic coastal and oceanographic features that dominate different survey regions. Outcomes from this work show that the spatial variability of oceanographic features should be taken into consideration before incorporating oceanographic indices in fishery stock assessment models. Highlights: Oceanographic indices used to describe variations in spanner crab catch rates were not homogenous throughout southern Queensland, Australia. Relationships were linked to region-specific coastal and oceanographic features that dominate different survey regions. Higher catch rates were linked to processes responsible for transporting oceanic waters into the various survey grounds. Enhanced surface chlorophyll a may increase predator aggregations, reducing the number of crabs available to the fishery. Regional oceanographic features should be considered before incorporating environmental indices in stock assessment models.