S2 File -

Humans alter ecosystems through both consumptive and non-consumptive effects. Consumptive effects occur through hunting, fishing and collecting, while non-consumptive effects occur due to the responses of wildlife to human presence. While marine conservation efforts have focused on reducing consumptive effects, managing human presence is also necessary to maintain and restore healthy ecosystems. Area closures and the tourism freeze related to the COVID-19 pandemic provided a unique natural experiment to measure the effects of decreased tourism on fish behavior in a high use no-take marine protected area (MPA) in Hawai`i. We found that when tourism shut down due to COVID restrictions in 2020, fish biomass increased and predatory species increased usage of shallow habitats, where tourists typically concentrate. When tourism resumed, fish biomass and habitat use returned to pre-pandemic levels. These displacement effects change fish community composition and biomass, which could affect key processes such as spawning, foraging and resting, and have knock-on effects that compromise ecosystem function and resilience. Managing non-consumptive uses, especially in heavily-visited MPAs, should be considered for sustainability of these ecosystems.</div

Changes in the fish community at Molokini.

Comparisons of fish biomass at all trophic levels among sampling periods from (A) long-term surveys and (C) DAR surveys. Box plots showing median (black line), mean (red line), upper and lower quartiles, and 5th and 95th percentiles. Principal coordinates analysis of fish assemblage composition based on biomass (g m-2) by sampling period for (B) long-term surveys and (D) DAR surveys. Data were ln(x+1)-transformed prior to analyses. Vectors are the relative contribution and direction of influence of fish taxa to the observed variation among sampling periods (Pearson Product movement > 0.5).</p

Monthly variation in the number of people visiting Molokini since 2013.

Circles show monthly counts of people at Molokini and are colored by quarters (q) that each corresponds to a 3-month period. The black line is the result of the GAM model. The yellow box denotes the period of travel restrictions associated with the COVID-19 pandemic (from March 2020 to May 2021).</p

Map of the study site, Molokini Shoal Marine Life Conservation District, located in Maui, Hawaii, USA.

Blue triangles show locations of acoustic tracking receivers, yellow and red dots show locations of fish surveys, yellow line shows the boundary of the no-fishing zone inside the crater, and red line shows the boundary of the trolling-only zone around the outside of the crater. Hillshade basemap derived from USGS Digital Elevation Model (DEM) [43]. The partially submerged volcanic crater that forms a wall around the interior is shown in the aerial photo (’Molokini Crater’ by Bossfrog from Wikimedia Commons under the Creative Commons Attribution-Share Alike 4.0 International license).</p

Fig 4 -

(A) Fish detections vs. presence of people at Molokini. Grey dots show detections per day for all Caranx melampygus vs. the daily count of people visiting the crater, with darker shade showing higher density. Red line shows GLM fit, grey envelope shows 95% confidence interval. (B) Diel behavior one C. melampygus (44 cm fork length) during 2020 and 2021. Y-axis shows diel cycle with time 00:00 (start of diel cycle) at bottom, noon at center and time 23:59 (end of diel cycle). Horizontal curves show dawn and dusk respectively. Dots show detections of C. melampygus with black representing inside the crater and red outside the crater. Yellow box indicates morning period of high human abundance. An interpretation guide for this figure is provided in the S1 Fig in S1 File.</p

Fish species observed in Nachvak Fjord.

num. m-2 = number of individuals per m-2, g m-2 = grams per m-2, Freq % = percent frequency of occurrence. Reported sizes (cm) are means, with minimum and maximum sizes in parentheses.</p

Dominant algal taxa and benthic cover by major habitat type in Nachvak Fjord.

Avg. (± sd) is average percent cover and one standard deviation. Percent contributions to average similarities within groups based on Bray-Curtis similarity matrices. % contrib. = percent contribution, % cum. contrib. = percent cumulative contribution.</p

Triplot of results of redundancy analysis on numerical abundance (num. m^-2) of megabenthic invertebrate feeding guilds by transect with biotic and abiotic variables (PC1, PC2, depth, salinity, temperature, habitat type, distance to mouth of fjord).

Predictor variables were centered and standardized, and megabenthic invertebrate feeding guild abundance data were centered and log(x+1)-transformed for analysis.</p

Table 12 -

(a) Results of redundancy analysis (RDA) on ln(x+1)‐transformed fish taxa abundance (num. m-2) by transect. (b) Conditional effects of Monte‐Carlo permutation results on the RDA.</p

Triplot of results of redundancy analysis on benthic taxa abundance by transect with biotic and abiotic variables (PC1, PC2, depth, salinity, water temperature, habitat type, distance to mouth of fjord).

Predictor variables were centered and standardized and megabenthic invertebrate taxa abundance was centered and log(x+1)-transformed for analysis.</p