Weighing the Fish

Weighing the Fish

Fish must be weighed on land with a certified scales or alternatively on a shop scales. If in doubt use a shop scales. Fish must not be weighed on board a boat. Scales must be certified annually by a competent independent authority and the certificate of accuracy must be current at the time of weighing. The ISFC recommended calibration service is NSAI. This certificate must accompany each claim application.

For ALL SPECIES ≤ 1 kg or ≤ 40 cm TL or FL, the fish must be weighed and claimed in grammes (g) and cm.

Weighing instruments and certification

The Committee insists that all fish be weighed on scales which are verified for accuracy. Shop scales normally used in trade are checked regularly by officers of the Legal Metrology Service (National Standards Authority of Ireland) and are acceptable for weighing specimen and record fish. Club or personalised (i.e. scales not normally certified by the Weights and Measures Authority for trade purposes) can be certified for accuracy. Such scales, if certified in advance by a reputable agency/company are acceptable to the Committee for weighing purposes. Certification will be valid for one year from the date of issue of the certificate of accuracy. The manufacturers certificate of accuracy will not suffice. Weights from scales which are not certified at the time of weighing or certified in retrospect will not be accepted.

Since 2012 the National Metrology Laboratory (NML), on request from ISFC, has provided a service to calibrate mechanical and digital fish scales (personal/club) based on EN 45501, from 0 – 100kg. The NML is the national metrology institute for Ireland and is responsible for establishing, maintaining and developing the national measurement standards for physical quantities and their dissemination to Irish users. NML operates as a division of NSAI (The National Standards Authority of Ireland).

Contact Details

Name:Rory Hanrahan
Address:NSAI National Metrology Laboratory,
Griffith Avenue Extension,
Dublin 9,
Tel:+353 (0)1 8082609


Since 2006, fish weights have been presented in kilograms in the Annual Report. Many anglers continue to use imperial measurements for fish and, recognising this, the ISFC decided to report in both metric (SI) and imperial metric systems since 2010. Claims will be accepted under either system unless legislation dictates otherwise.

Weight conversion figures

The ISFC decided to use the metric system (kg) for reporting from 2006 onwards, although some older record fish will be reported in the imperial system until a new record is set.
To aid anglers in the conversion between both systems conversion factors are provided below. Alternatively, anglers can use the weight converter calculated, located at the top right of this page.

Kilogrammes to pounds: X kg divided by 0.454 = Y metric pounds
Pounds to kilogrammes: X lbs divided by 2.205 = Y kg

Review of Specimen Weights

In 2009 the ISFC began to systematically review all species and weights of specimen fish based on the data collated since the ISFC was established. This process aims to reflect current developments in specimen angling and other issues including conservation. This process was carried out for some species in recent years (e.g. Coalfish in 2006 and 2007). Factors taken into account included the number of specimens taken per annum, the geographical distribution of specimens around Ireland and trends in the numbers taken over different periods. In 2010 the review was completed (from Garfish (B. svetovidovi) to Cuckoo Wrasse) and resulted in reductions in specimen weights for some species, several of which had not been adjusted since the ISFC was founded. Specimen weights were reduced for three of the eighteen fish categories in freshwater (16.7%) and 15 of 69 marine species (21.7%).

this process is ongoing and anglers are advised to consult with the table of specimen weight presented in this website and in the Specimen Fish Reports to keep up to date with changes.