Standardised indices for longfin and shortfin elvers were estimated and compared with indices generated from catch at Karapiro, Matahina, Pātea, and Wairua dams. Modelled longfin elver indices contrasted with catch indices generated from Karapiro, Matahina, Wairua, and Pātea dams. Modelled shortfin elver indices closely followed catch indices at Karapiro. Shortfin catch indices from Matahina, Wairua, and Pātea dams initially followed modelled indices but then deviated later in the time series.

This report describes trawl and acoustic biomass surveys of orange roughy undertaken on the south-west Challenger Plateau in ORH 7A and adjoining Westpac Bank aboard FV Thomas Harrison during June-July 2018.

An alternate-tow approach for evaluating performance of the Modular Harvest System relative to a mesh trawl was tested. GLMM and bootstrapping approaches were both suitable for comparing catch rates. Several methods for comparing fish size composition were evaluated. Relative selectivity was more informative than proportions below a specific length. Despite a sample size of 11 tow pairs, data collected during the trial were sufficient to demonstrate some clear differences between the gears.

A comparison of mesh trawls and the Modular Harvest System (MHS) in the hoki fishery off the North Island east coast allowed differences in catch rates and the relative selectivity to be assessed for hoki, gemfish, and ling. Catch rates of gemfish were significantly lower with the MHS. The MHS caught significantly fewer hoki in the 65 cm to 85 cm range, although the differences in proportional catch at length were generally not significant after accounting for differences in fishing power.