DOI: 10.5061/dryad.1zcrjdft7
title: Effects of harvesting on subtidal kelp forests (Lessonia trabeculata) in Central Chile

description: The systematic degradation of marine ecosystems is a global phenomenon
 that has important and diverse consequences including biodiversity loss
 and reduced ecosystem service provisions. In temperate regions, subtidal
 kelp forests are dominant ecosystems in rocky coasts, subjected to the
 influence of local-scale stressors and regional environmental variation.
 For example, kelps within the Humboldt Current System are at risk of
 degradation from live-harvesting by fisheries. However, limited
 information exists regarding the long-term consequences of kelp harvesting
 which, in turn, limits the ability to provide effective management and
 conservation efforts. Here, we examined the ecosystem-level consequences
 of the artisanal subtidal Lessonia trabeculata fishery
 along the coast of central Chile during a two-year period, assessing a)
 the change in adult and juvenile L. trabeculata density
 within harvested and non-harvested (control) plots (~90m2), b) the impact
 of L. trabeculata harvesting on reef fish and
 macroinvertebrate assemblages, and c) the change in density of the most
 abundant L. trabeculata-associated species. The experiment was
 conducted over a two-year period, from December 2016 to May 2019.
 Approximately 90% of L. trabeculata was removed by an
 experienced kelp fisherman in experimental plots. After two
 years, L. trabeculata and its associated community
 showed a lack of recovery in the harvested plots. Within these plots, the
 average abundance of the rock shrimp, Rhynchocinetes
 typus, and the herbivorous snail, Tegula
 tridentata, was greater than in non-harvested plots and the
 pattern persisted over the study period. The difference in abundance of
 associated species may be key to the (lack of) recovery of L.
 trabeculata forests. Our study highlights the impact
 of L. trabeculata harvesting on associated fauna,
 however, significant knowledge gaps remain regarding the capacity and time
 frame to re-establish the original biomass of L. trabeculata, as
 well as its associated fauna. The management of L.
 trabeculata fisheries needs to account for ecosystem-wide impacts
 in order to better manage and protect vital coastal ecosystems.
description: Experimental plots were monitored 6 times between December 2016 and May 2019. The first monitoring was conducted immediately prior to the harvesting (Pre) in order to provide baseline information on each plot. Afterwards, monitoring was conducted every three months during the first year and then two-years after the kelp was harvested. At each sampling time, one 25-m transect was deployed within each plot and surveys of various portions of the transect alongside quadrats of varying size and placement interval (based on the size and mobility of target organisms/species) were conducted by SCUBA divers. When the transect extended beyond the edge of harvested plots, only the harvested portion of the transect was monitored. All data was standardized according to the sampled surface area in order to ensure comparability of measurements across treatments. The density of adult (holdfast diameter ≥ 10 cm) and juvenile (&lt; 10 cm) <i>L. trabeculata</i> sporophytes were estimated using the standard transect-quadrat method. Kelp <i>L. trabeculata</i> density was estimated in at least five 1 m<sup>2</sup> quadrats that were placed every two meters over a transect placed at the center of each plot. In addition, the holdfast diameter, number of stipes, length (from base of holdfast to tip of stipe), and the foliage index of the canopy was recorded for each <i>L. trabeculata</i> sporophyte found within the quadrats. The foliage index is a visual estimate of the percentage of stipes containing blades with values ranging from 1 to 5 according to the following categories: 1 &lt; 10%, 2 = 10 - 30 %, 3 = 30 - 50%, 4 = 50 - 80%, 5 = 80 -100% (see Pérez-Matus et al. 2017a for further information). The density of mobile benthic macroinvertebrates (&gt; 1 cm) were estimated by visual counts in at least five 2 m<sup>2</sup> quadrats in the same transect where kelp was measured. In each quadrat, individuals were identified to the lowest possible taxonomic level. In two monitoring occasions (at 12 and 24 months post-harvesting), the percentage cover of macroscopic sessile invertebrate species (e.g. hydrozoans, macroalgae, barnacles, sponges) was also quantified in ten<i> </i>0.25 m<sup>2</sup> quadrats placed randomly within each plot. The percent cover of bare space (i.e. substrate free of macrobenthic species) was also quantified. In the case of organisms impossible to identify <i>in situ</i>, samples were taken for subsequent identification in the laboratory.  Reef fishes were quantified using underwater visual census (UVC) along a 25 m transect placed at each plot. Along each transect, a diver registered the identity of each fish encountered within a 4 m wide and 5 m tall "tunnel". Common cryptic fish fauna (e.g. Blennidae, Labrisomidae, Clinidae, Trypterigidae) were quantified along the same transect but in a 2 m wide section (5 m tall; 250 m<sup>3</sup>). Fish surveys were conducted pre-harvesting and 6, 12 and 24 months post-harvesting.However, after harvesting event the UVC was performed only in the harvested section in the harvested plots therefore the transect length was reduced to ~11-15 m in length.   Abiotic conditions including depth, slope and surface rugosity of each plot were estimated. Depth was recorded at each quadrat while the bottom slope was calculated as change in depth over length of transect. Bottom rugosity, an indicator of seafloor habitat complexity, was estimated by randomly placing a 4 m long, small link chain (1 cm per link) along a central area of each plot, ensuring it followed the topography of the substrate. The linear horizontal distance between the extremes of the chain provided a rugosity index. This measurement was repeated three times per plot and the average rugosity index was calculated. 
description: 6 different sheets are uploaded:  Spread
 Sheet    Spread Sheet description<br> 1. Spp_DB    Data base of the
 average abundance for each taxa, standardized per unit of
 observation<br> 1. Spp_DB    Data base of the average abundance for
 each taxa, standardized per unit of observation<br> 1. Spp_DB  
  Data base of the average abundance for each taxa, standardized per unit
 of observation<br> 1. Spp_DB    Data base of the average abundance
 for each taxa, standardized per unit of observation<br> 1. Spp_DB  
  Data base of the average abundance for each taxa, standardized per unit
 of observation<br> 2. Slope_DB    Data base of the slope observed in
 each plot<br> 2. Slope_DB    Data base of the slope observed in each
 plot<br> 3. Rugosity_DB    Data base of the surface rugosity
 observed in each plot<br> 3. Rugosity_DB    Data base of the surface
 rugosity observed in each plot<br> 3. Rugosity_DB    Data base of
 the surface rugosity observed in each plot<br> 4. Depth_DB    Data
 base of the average depth observed in each plot<br> 4. Depth_DB  
  Data base of the average depth observed in each plot<br> 5. Kelp
 Morphology    Data base of the kelp forest characterization observed in
 each plot<br> 5. Kelp Morphology    Data base of the kelp forest
 characterization observed in each plot<br> 5. Kelp Morphology  
  Data base of the kelp forest characterization observed in each
 plot<br> 5. Kelp Morphology    Data base of the kelp forest
 characterization observed in each plot<br> 5. Kelp Morphology  
  Data base of the kelp forest characterization observed in each
 plot<br> 6. Readme Column
 Column description<br> A-C    Sampling Time, Treatment and
 Plot Identification<br> D-E    Kelp density data in: individuals *
 m-2<br> F-AU    Mobile Benthic Macroinvertebrates density data in:
 individuals * m-2<br> AV-BS    Sessile Kelp Understory species
 coverage data in: %<br> BT-CL    Reef Fish density data in:
 individuals * m-3<br> A-C    Sampling Time, Treatment and Plot
 Identification<br> D    Estimated slope of the plot<br> A-C  
  Sampling Time, Treatment and Plot Identification<br> D    N° of
 Replicate within each plot<br> E    Observed chain length once it
 was placed over the seafloor<br> A-C    Sampling Time, Treatment and
 Plot Identification<br> D    Average depth of the plot<br>
 A-C    Sampling Time, Treatment and Plot Identification<br> D  
  Average Holdfast Diameter within each plot, meassured as the maximum
 observed diameter<br> E    Average N° of Stipes per kelp within each
 plot<br> F    Average Foliage Index per kelp within each
 plot<br> G    Average Height per kelp within each plot, measured in
 a straight line from the holdfast up to the top of canopy