D'Arcy Webber

• Doctor of Philosophy
• Consultant at Quantifish Limited

This document describes the lobster stock dynamics (LSD) model: a size-structured model specifically designed for developing stock assessments of red rock lobsters (Jasus edwardsii) in New Zealand. The LSD model tracks the numbers of individuals in discrete size classes for three different sex / maturity categories (i.e., males, immature females, a...

To assess and manage fisheries risks across large numbers of non-target populations, potentially impacted by multiple threats, fisheries managers are forced to make difficult decisions in the context of poor and/or sparse information. Thus, innovative methods are required to enable maximum use of available data. To this end, MPI has developed the S...

This document describes a new stock assessment of red rock lobsters (Jasus edwardsii) in CRA 6, the Chatham Islands. The length-structured stock assessment used the lobster stock dynamics (LSD) model. Data manipulation and technical decisions were discussed by the Rock Lobster Fishery Assessment Working Group who oversaw the stock assessment. The...

Executive Summary Project 68 aims to: estimate total annual seabird mortalities in WCPFC fisheries; assess mortality per year since the first WCFPC seabird CMM and assess whether there is any detectable trend; describe the methods used, including treatment of data gaps; identify limitations in available data; and, given available data, generate adv...

This document describes the management procedures used for the 2018–19 fishing year to manage New Zealand stocks of red rock lobsters (Jasus edwardsii). Management procedures are simulation-tested decision rules. Given an input (e.g. offset year CPUE) they return an output (e.g. Total Allowable Commercial Catch, TACC). They consist of a harvest con...

This document describes a new stock assessment of red rock lobsters (Jasus edwardsii) in CRA 2 and a review of operational management procedure evaluations. The stock assessment was done using the lobster stock dynamics (LSD) model. The Rock Lobster Fishery Assessment Working Group oversaw this work: data files and all technical decisions were agr...

Nearly half of the freshwater discharge into the Gulf of Alaska originates from landscapes draining glacier runoff, but the influence of the influx of riverine organic matter on the trophodynamics of coastal marine food webs is not well understood. We quantified the ecological impact of riverine organic matter subsidies to glacier-marine habitats b...

The history and management of the New Zealand fishery for the rock lobster Jasus edwardsii is described. The fishery was essentially open-access to 1979, with limited input controls. Access was strictly limited from 1979 to 1989, but effort increased to a peak in 1985, when the fishery was fully exploited. Early stock assessments suggested over-exp...

Organisms in the marine environment are likely to exhibit variation in growth rates among individuals, and this variation may be persistent (particular individuals growing faster/slower throughout their entire lifetime) or transient (particular individuals growing faster in one year than another year). Understanding variation in growth is necessary...

Complex fisheries models, such as individual-based or spatially-explicit models, provide a potential framework for exploring complex dynamics in populations, communities and ecosystems. Inference that ignores individual variability and/or spatial complexity may provide biased, imprecise or overly-precise platforms for management advice. However, st...

Stock assessments rely on estimates of total mortality resulting from fishing activities. However, fish that are captured by fishing gear that is not subsequently retrieved are generally not counted in estimates of total fishing removals or otherwise accounted for in stock assessment models. The mortality resulting from the loss of sections of bott...

This thesis is about the demography of the tunicate Styela clava, a species of some notoriety because of its invasiveness and impacts in many parts of the world. Species assemblages have continuously changed throughout evolutionary history, but the rate of today’s anthropogenically facilitated dispersal is unparalleled in history. Non-indigenous sp...