FRV Mara 9/71
Cruise summary report
| Cruise Info. | |
| Ship name (ship code) | FRV Mara (74MR) |
| Cruise identifier | 9/71 |
| Cruise period | 1971-08-09 — 1971-09-24 |
| Status | Completed |
| Port of departure | Portnaguran, United Kingdom |
| Port of return | Stornoway, United Kingdom |
| Purpose | Research |
| Objectives | Behaviour:
1. Observation, recording and photography by divers of the behaviour of flatfish during the process of demersal seining will be carried out. 2. The light weight trawl camera will be used attached to the headline to take a regular sequence of pictures of the area in front of the groundline. 3. Flatfish will be tagged to determine behaviour in relation to tide, and for the estimation of the catching efficiency of the gear. 4. If haddock are seen at any stage during the operation, the opportunity will be taken to make observations upon them. The underwater tagging team will tag as many haddock as possible after the detachment of the codend prior to hauling the gear to the surface. Gear: 1. Wing end and deck tensions will be recorded by instruments. The deck tension meter may not be made available until part way through the cruise, and arrangements will be made at the time for fitting apparatus. 2. Photographs will be taken from a fixed position on the boat deck to record the rope divergence and declination. 3. One diver will make periodic estimates of headline height and curvature. Photographs will be taken with a fish-eye lens in an attempt to get an accurate estimate of headline curvature. 4. A direct reading current meter will be used before and after each haul. 'Mara' will be required to maintain a fixed position at anchor whilst these readings are being taken. 5. Flowmeters will be used on the net and from 'Mara' to obtain ship and net speeds. Photometry: 1. Surface illuminance will be continuously recorded during hauls, and intermittent readings taken of underwater illuminance to determine attenuation. 2. A sighting range will be set up on the bottom of Portnaguran; this will be used for underwater visibility experiments as fishing operations permit. 'Mara' will be required to lay a temporary mooring nearby using a spare anchor, in order that light metres can be used from the ship. |
| Chief scientist | C C Hemmings (Department of Agriculture and Fisheries for Scotland Aberdeen Marine Laboratory) |
| Cruise report |  (0.22 MB) |
| Ocean/sea areas | |
| General | North Sea |
| Measurements | |
| Physical oceanography | |
| Optics (eg underwater light levels) | Description: optical properties |
| Biology and fisheries | |
| Gear research | Description: instrument development |
