Marine Scotland

Where do fish live?

October 23, 2017 by No Comments

Last week,  our scientists were involved in a programme aimed at providing fine-scale data on the habitat associations of cod, haddock and whiting at a key period in their life history – following the transition from pelagic to demersal habitat.

The programme also provided them with an opportunity to add to the fish trap and fixed-position baited underwater video data obtained earlier in the year, which is used to further inform 0-group distribution models and samples for otolith-based growth and survivorship analysis.

During the programme, which was conducted on board the MRV Lady Nicola, scientists deployed fish traps over various habitat types within and around the Small Isles MPA and also synchronously deployed baited remote underwater video camera frames fitted with twin cameras calibrated for post-survey photogrammetric analysis.

Fish traps were deployed at the start of each working day, in fleets of 3, 2 and 2 traps, to be picked up again following a minimum soak time of 6 hours. The deployment location (GPS latitude and longitude), soak time, and bait type and quantity were recorded and captured fish released from the trap, with measurements of total length (to 1 cm) and weight (to 0.01 g). Otoliths from gadoid species (cod, haddock, and whiting) were also extracted to establish age, with tissue from a subsample of the catch and stored in ethanol for genetic analysis. Time was set aside during each day to collect fresh bait.

Both underwater video camera frames were deployed at distances sufficient to avoid any interaction with the fleet ground gear (recommended minimum 500 m between deployments). Two cameras oriented ±6° perpendicular to the frame base were synchronously recording high definition video for a nominal period of 1.5 hours. Footage was then downloaded to external media at the end of each working day. Species type, relative species densities (MaxN) and substrate type (assessed visually) were classified post-survey.

Table 1: Latitude, longitude & habitat variables of potential survey stations.

Station Substrate Longitude Latitude (dd) Longitude Latitude Depth (m)
1 Rock & Other Hard Substrata -6.47643 57.05647 006° 28.58596′ W 057° 33.87997′ N 48.4
12 Mixed -6.4066 57.05017 006° 24.39607′ W 057° 30.10482′ N 62.8
20 Sandy Mud – Muddy Sand -6.5747 56.92952 006° 34.48182′ W 056° 55.77110′ N 88.7
24 Sand -6.20849 57.01463 006° 12.50945′ W 057° 08.77659′ N 50.8
7 Coarse/Mixed Sediments -6.39688 56.95936 006° 23.81250′ W 056° 57.56159′ N 49.2
8 Mud -6.56517 57.0306 006° 33.91008′ W 057° 18.35910′ N 69.7
SI_01 Rock/Biogenic Reef -6.60639 57.0602 006° 36.38324′ W 057° 36.11881′ N 16.1
SI_02 Rock/Biogenic Reef -6.57409 57.06484 006° 34.44535′ W 057° 38.90486′ N 13
SI_03 Rock/Biogenic Reef -6.53778 57.07331 006° 32.26683′ W 057° 43.98393′ N 24.4
SI_04 Rock/Biogenic Reef -6.49853 57.07099 006° 29.91172′ W 057° 42.59426′ N 22.5
SI_05 -6.58524 57.04178 006° 35.11412′ W 057° 25.06538′ N 9.9
SI_06 -6.55298 57.04953 006° 33.17855′ W 057° 29.72089′ N 5.2
SI_07 -6.52064 57.05089 006° 31.23856′ W 057° 30.53686′ N 2.9
SI_08 -6.49293 57.04335 006° 29.57559′ W 057° 26.00770′ N 13.1
SI_09 Coarse/Mixed Sediments -6.37188 57.05886 006° 22.31260′ W 057° 35.31412′ N 31.1
SI_10 Rock/Biogenic Reef -6.40763 57.03812 006° 24.45761′ W 057° 22.86995′ N 20.9
SI_11 Rock/Biogenic Reef -6.43775 57.02183 006° 26.26522′ W 057° 13.09882′ N 16.7
SI_12 Rock/Biogenic Reef -6.46154 57.01092 006° 27.69257′ W 057° 06.55039′ N 32.4
SI_13 -6.43177 56.99241 006° 25.90618′ W 056° 59.54469′ N 6
SI_14 Rock/Biogenic Reef -6.41057 56.98095 006° 24.63396′ W 056° 58.85701′ N 15.9
SI_15 -6.35911 56.94771 006° 21.54636′ W 056° 56.86235′ N 19.5
SI_16 Sand -6.29011 57.04751 006° 17.40676′ W 057° 28.50321′ N 12.1
SI_17 Sand -6.2573 57.03721 006° 15.43800′ W 057° 22.32887′ N 24.8
SI_18 Sand -6.24367 57.02166 006° 14.62042′ W 057° 12.99781′ N 22.6
SI_19 Sand -6.23116 57.00311 006° 13.86964′ W 057° 18.64878′ N 43.2

Further Information:


Tags: , , , ,

Comments

Leave a comment

Your email address will not be published. Required fields are marked *