Development Roadmap

This document records what SPoRC development is working towards, what is saved for later to be revisited, and what is likely not in the development plan (out of scope) .

Four tracks are likely to be developed in the future: numbers at age as a state space process, close-kin mark-recapture, electronic tagging, and process error on the remaining parameter blocks.

Work to date has involved the following released versions:

Released versions

Version	Date	What it added
1.0.0	2025-11-24	First public release. Age, sex, season and region structured dynamics, closed loop simulation and management strategy evaluation.
1.1.0	2026-03-31	Movement estimated as a continuous time Markov chain with preference functions.
1.2.0.9000	in development	Population specific (natal homing) and seasonal dynamics, discarding and retention, time varying and semi-parametric growth, conditional age at length, at age data sources, estimated index observation error, per fleet ageing error.

Numbers at age as a state space process

Recruitment is the only stochastic element of the population state. From age 2 onwards, numbers at age are a deterministic consequence of recruitment, mortality and movement, so any misspecification in natural mortality, in selectivity or in the reported catch is absorbed by the recruitment deviations. Estimating process error on the whole numbers at age surface, as in SAM and WHAM, lets that misspecification enter at the age it occurs instead. (This has now been implemented).

Close-kin mark-recapture

Close-kin mark-recapture estimates absolute abundance from the rate at which pairs of sampled fish turn out to be related. The quantities it needs are already in the report file: numbers at age by population, region, year and sex, maturity at age, and weight at age, from which relative reproductive output follows. What is missing is the pairwise comparison data and a likelihood over it.

Electronic tagging

Conventional tags inform movement through recaptures. Recaptures are sparse, they happen only where the fishery is, and they arrive filtered through a reporting rate. Archival and satellite tags record position through the fish’s life independently of the fishery, so they inform the movement rates themselves rather than the movement rates confounded with fishing processes.

Process error on the remaining parameter blocks

Selectivity and growth already take a deviation surface with a choice of covariance, and fishing mortality takes independent, random walk or first order autoregressive deviations. Natural mortality and catchability are constant within a time block, and regional recruitment deviations are independent. Thus, another priority of SPoRC will be to add additional process error functionality to these data sources.

To be revisited

Environmental covariates on recruitment, natural mortality, growth and catchability. Movement already accepts covariates through cont_vary_movement, and extending the same interface to the other processes is a natural addition. It is not a near term priority and will be revisited.

Outside current scope

Capability	Rationale
Multispecies models and predation mortality	SPoRC is designed for single-species population dynamics, potentially with multiple populations or regions. Multispecies interactions and predation mortality are therefore outside the current scope of the framework.
Fully length-structured dynamics	SPoRC uses age as the primary population-structure dimension. Length-based observations and selectivity can be represented through age–length relationships without requiring the population dynamics themselves to be fully length structured. A fully length-structured implementation would substantially expand the model structure and computational burden without being necessary for the primary applications of SPoRC.
Hermaphroditism and sex change	SPoRC assumes sex is fixed after recruitment. Given that hermaphroditism and sex change are relevant to relatively few species and are not a primary focus of the intended applications, they are outside the current scope of the framework.