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Координационная рабочая группа по статистике рыбного хозяйства

Catch and landings

The overall aim for statistics on catch and landings is to report on fisheries contribution to the national economy, to the provision of food (subsistence) and on the total removal of fish and shellfish from the sea. Catch Statistics are internationally reported as "NOMINAL CATCHES" which refers to the landings converted to a live weight basis. However, fisheries impact on the ecosystem goes beyond the landed fish and shellfish and includes fish and organisms impacted by the gear. Some of these are brought on deck and later discarded.

The various concepts (Fish, shellfish and organisms encountering a fishing gear, GROSS REMOVAL, PRODUCT WEIGHT, LIVE WEIGHT, NOMINAL WEIGHT and various forms of loss) are described in the catch concept diagram. There are examples where in addition to the catch in weight also the number of individuals caught is required.

Catch and landing statistics are for many purposes required as very detailed data e.g. broken down by fleet, gear, season and detailed area. The nationality of landings follows the vessel flag state principle as described in Nationality of Catch and Landings.

National and Regional fisheries organisations publish annually catch statistics in different forms. These statistics are available from the websites of these organisations. FAO publishes global fisheries statistics. These statistics are summarised in "FAO Statistical Yearbooks" and are available in more details from the FAO Fisheries and Aquaculture Statistics website. When using published catch and landing statistics it is to be recognised that non-reporting of landings is a major concern in some fisheries.

Nominal catches

The concept "NOMINAL CATCHES" refers to the landings converted to a live weight basis. In fact it is often referred to as the "Live weight equivalent of the landings" or shortened to the "LIVE WEIGHT". In national publications the same concept is also given the name "Landings on a round, fresh basis", "Landings on a round, whole basis" or "Landings on an ex-water basis". Thus often , in further processing the data, conversion factors are applied to the individual products which express the weight in a more homogenous way.

Care should be taken when referring to the NOMINAL CATCH (the live weight equivalent of the landings) as the CATCH, since in many situations the initial catch (the GROSS CATCH) has been reduced by a number of factors. These factors are best illustrated in the catch concept diagrams.

Landed weight

The concept "LANDED WEIGHT" refers to the mass (or weight) of a product at the time of landing, regardless of the state in which is landed. That is, the fish may be whole, or gutted or filleted. Consequently this unit is of limited use for further analysis except where it is known that the product is very homogenous in nature. Where more detailed analysis of the data is required the landed weight is generally converted to a more meaningful measure, the most frequently used being the "Nominal catch". The landed weight is relevant in economic analysis being the one to which first-hand sales prices refer.

Product weight

The concept "PRODUCT WEIGHT" is the weight of a product at the time of weighing. Thus it does not describe the presentation of the product and, unless it is known that the product is homogenous in form, further analysis has to proceed with caution. As for landed weight relevant when calculating the value of the catch.

NOMINAL CATCH is most often not obtained as a direct measure but has to be derived and this is usually done by applying a conversion factor to the landed weight.

Discards

Discards are fish and organisms that are returned to the sea during sorting the catch on board. The reasons for discarding are many including lack of market opportunities, damaged fish, fish with wounds or cuts or infected by parasites, undersized and non-commercial fish species and organisms, high grading. These data are recorded at sea by observers or inspectors and measured as fresh weight.  Discarding is banned in several fisheries.

Logbooks provide estimates of the catch at sea and for many industrialised fisheries logbook information is available and may be used for a direct estimate of the catch. However, the accuracy of measures recorded on fishing log-sheets depends on available weighing technology and/or the experience of the observer in making a visual assessment of the volume and composition of a catch - Section Logbooks and VMS.

Non-reporting of landings is a major concern in some fisheries. Many national statistical publications do not use the terms "catch" and "landings" with the precise meanings as described in this section. In such publications "catches" may in fact refer to the "landings" and be expressed on a landed weight basis. However, only where the primary production (used in the economic and not the biological sense) is landed whole it is correct to refer to such quantities as "catches".