Number (N) of wooden fishes estimated with the Distance Sampling (DS) method by the experienced and non-experienced divers for the total census area (3000 m²) and the confidence interval (N CI 95%) at p < 0.05.

<p>DS estimator: the best fit from the nine estimators tested with the DISTANCE software. D = Density per 300 m2. %CV = Coefficient of variation of the estimation in percentage. N detected (%) = Number of wooden fishes detected by divers and the percentage of the total wooden fish. MDD = Mean distance detection derived from visual estimations and standard deviation (SD) by divers. "*" Actual number of wooden fishes. "**" Actual mean distance.</p

Density estimations (D) (fish/300m²) and coefficients of variations (CV) for studied species and the total of groupers for different combinations of transects types and census widths in Cabo de Palos and Cabo Tiñoso.

<p>Note that CST values in Cabo Tiñoso were derived from simulations. CST = Conventional Strip Transect. TRT = Tracked Roaming Transect. FW3 and FW10 = Fixed Width of 3 and 10 m for each side of the transects, respectively. DS = Distance Sampling Method. The census area of each survey is detailed in m² considering total transect lengths and 6 and 20 m width for FW´s estimators and 40 m width for the DS estimator.</p

Scheme of the count method using the Distance Sampling method.

<p>IL = imaginary line. X^1-2 = perpendicular distances of solitary individuals to the transect line. X³ = perpendicular distance of a school of fishes to the perpendicular line. The equipment (Fig 2) is illustrated above divers, like at the surface. Inset: The Tracked Roaming Transect equipment. A = Waterproof case for GPS. B = Body Board Slate. C = Diving reel. D = Weight.</p

Study sites.

<p>(A) Islas Hormigas and Hormigon in Cabo de Palos Marine Reserve (37.6550° N -0.6497° E). The distance between islands is not to scale to ease the representation. (B) Cabo Tiñoso (37.5370° N -1.1419° E). Straight lines: 50-m Conventional Strip Transects. Curved lines: Tracks of the Tracked Roaming Transects.</p