Description

Length frequency is defined by UN ESCWA as the number of individuals of a catch or catch sample in each length interval. The modal size is the length group with the higher number of individuals.

Length frequency refers to individual body lengths (or weights) of species per fleet, fishery, year, gear, type of school, month and spatial areas

This form supports the reporting of estimates of sample size taken by number (or weight) for a given CPC / fleet.

Resources

Length frequency data could be reported: - by individual fishery and species through the single form 4-SF; - or for multiple fisheries and species using the form 4-SF multiple. Contrary to single 4-SF form, where data specifications are to be defined in the metadata worksheet, in the 4-SF multiple these are listed in the data worksheet to align the data with specifications for each fisheries and species.

return back to the list of all IOTC statistical data reporting forms.

Supported resolutions

  • 15/02 - Mandatory statistical reporting requirements for IOTC Contracting Parties and Cooperating Non-contracting Parties (CPCs)
  • 17/05 - On the conservation of sharks caught in association with fisheries managed by IOTC
  • 19/03 - On the conservation of mobulid rays caught in association with fisheries in the IOTC area of competence
  • 12/04 - On the conservation of marine turtles
  • 12/06 - On reducing the incidental bycatch of seabirds in longline fisheries
  • 23/06 - On the conservation of cetaceans
  • 13/05 - On the conservation of whale sharks (Rhincodon typus)

Reference species groups

  • IOTC species [ mandatory ]
  • Sharks [ mandatory ]
  • Mobulids and rays [ mandatory ]
  • Other bycatch / non-IOTC species [ voluntary ]

Reporting deadlines

  • Longline fisheries: 30 June (preliminary), 30 December (final)
  • Surface fisheries: 30 June (final)
  • Coastal fisheries: 30 June (final)

Stratification

Main data fields

  • Month (mandatory)
  • IOTC regular grids
  • Fishery
  • Species
  • Sex
  • Size class (Low)
  • Size interval
  • Number of samples (raw number of samples)
  • Number of fish measured (raised number of samples)

Additional data fields

Referenced codelists

Administrative and geospatial domains

Countries (ADM.COU)

Reference codes modeling the flag / reporting country submitting a dataset to the IOTC Secretariat.

IOTC regular grids (GIS.IOTC.CESF)

Codes for all 1°x1° and 5°x5° grids that overlap - at least partially - with the IOTC convention area.

Due to to the large size of the dataset, this is not included for filtering / browsing, but can be directly downloaded as a CSV from here: IOTC_GRIDS_CE_SF.

Fisheries and fishing technologies domains

Fisheries (FIS)

An ad-hoc classification derived from a combination of several factors (purpose, area of operation, vessel size category, gear, gear configuration, fishing mode and target species) that uniquely describe fishing practices for groups of vessels.

An interactive wizard to help CPCs identify the IOTC code for their fisheries (among those currently considered of relevance in the Indian Ocean).

Biological and morphometrics domains

Measurement type (MOR.MTY)

Reference codes that model the measurement types as lengths or weights collected as the size frequency.

Measurement tools (MOR.MTO)

Reference codes that model the measurement tools, combining those specific for individual lengths and weights used to measure individual species.

Measurement types (MOR.MES))

Reference codes that model the measurement types, combining those specific for individual lengths and weights used to measure individual species.

Type of fate (SPC.FTT)

Reference codes used to identify fate as indicating that the fish has been retained or discarded.

Fates (SPC.FTE.*)

Reference codes used to identify fate combined the reasons for retain and those for discard.

All species (SPC.ALL)

Reference codes modeling the species interacting with the fisheries as:

  • target species (retained or discarded)
  • bycatch species (retained or discarded)
  • sampled individuals
  • etc.

These codelists are subsets of the entries in the ASFIS list of species for fishery statistics purposes, from which they inherit the alphabetic codes, English, French and scientific names, as well as the family and order, and add the species category (in the IOTC sense), the IUCN status (retrieved from the IUCN red list of endangered species) and other characteristics of each entry such as their status of single species / species aggregate, bait species, SSI species, IOTC species.

Data and metadata domains

Data types (DTA.TY)

Reference codes modeling the type of statistics provided through a specific form, and in particular if these are:

  1. preliminary if the statistics were estimated by using some information from the fishery and year concerned, and the data reported are likely to change in the future as more information become available; or
  2. final if the statistics were estimated by using the complete set of data from the fishery and year concerned, and the data reported are unlikely to change in the future.

Data raising (DTA.RA)

Reference codes modeling the level of raising applied to the data (raised to totals / not raised to totals / unknown).

Size-frequency data sources (DTA.SRC.SF)

Reference codes modeling the source of the data provided through the size-frequency data form

Size-frequency data processings (DTA.PRO.SF)

Reference codes modeling the processing applied to the data provided through the size-frequency data form.

Coverage types (DTA.COV.TY)

Reference codes modeling the type of coverage for the raw information used to obtain the data provided through a specific form.