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The uninhabited Northwestern Hawaiian Islands (NWHI) contain 70 % of the shallow water coral reefs in the United States. An estimated 52 metric tons of derelict fishing nets accumulate here annually, becoming entangled in the reef structure and reducing coral cover. Here, we investigated the longevity of derelict net impacts on coral reef communities three years after net removal at Pearl and Hermes Atoll. Structure-from-Motion technology was used to resurvey net impact and control sites to determine whether coral cover rebounded at impact sites over time. Our results showed significantly lower coral cover at impact sites. Much of the bare substrate immediately exposed after net removal was also colonized by algae —not reef calcifiers. Continued monitoring of these sites will add clarity to the lasting nature of derelict nets on reefs, and supplementing net removal efforts with active restoration activities may assist in restoring the ecosystem function of impacted sites faster. • Benthic impacts of derelict nets persist on reefs three years after net removal • Coral cover reduced at net impacted sites compared to controls • Bare substrate after removal colonized by algae over time—not by reef calcifiers • Continued monitoring needed to determine lasting nature of derelict nets on reefs • Supplement net removal effort with restoration to restore ecosystem function faster [ABSTRACT FROM AUTHOR]

Rocky reefs in the temperate Northeast Pacific constitute a small portion of the nearshore seabed, yet are highly valued as productive habitat for local fisheries. Surveying these structurally complex, untrawlable habitats requires robust gear that can be deployed in rough sea states. Here, a cost-effective, compact video lander was evaluated for its ability to survey the diversity and abundance of nearshore (< 40 m), rocky-reef-associated fish populations (e.g. Sebastes, Cottidae, Hexagrammidae). To determine the application and limitations of surveying complex rocky reefs with this new tool, this study sought to (1) determine the frequency of observation of known nearshore fish species, (2) evaluate the influence of baiting the lander on the observed fish assemblage, (3) identify the optimal deployment time to maximize observed species richness and abundance, and (4) evaluate species-specific behavioral responses to the lander characterized a priori as attractive, avoidance, or neutral. Seventy percent of lander deployments met established requirements of visibility, view, and habitat. Seventy-seven percent of observed fishes were identifiable to species. The method observed 15 species belonging to 5 families; 5 species were classified as common (observed in > 20% of deployments), the remaining rare. Contrary to lander studies in other regions, bait was not found to improve species-specific identification, increase observed species richness or abundance (at the species or feeding guild level), or shorten deployment duration. A deployment time of 8 min on the benthos was determined as optimal for observing maximum species richness and abundance in the nearshore, doubling the previously described lander drop durations evaluated in deeper Oregon, U.S.A., waters. Species-specific behavioral responses to this compact lander were evaluated by viewing trends in species abundance (assessed within 30 s bins) over the deployment duration; no attractive or avoidance behaviors were observed. Results confirm that this simple, cost-effective video lander configuration is suitable for sampling the suite of fish species found in the nearshore, including rockfish species federally designated as “overfished” ( Sebastes pinniger and Sebastes ruberrimus) . Furthermore, this study illustrates the importance of evaluating the performance of survey tools in the specific environment in which the tool will be used to determine best-practices from long-term monitoring. [ABSTRACT FROM AUTHOR]

Derelict fishing nets pose hazards to marine systems as they travel through the ocean or become ensnared on coral reefs. Understanding of the movement of nets within shallow atolls can help to optimize operations to protect these shallow reefs. In 2018, six derelict fishing nets at Manawai (Pearl and Hermes Reef) in the Northwestern Hawaiian Islands were tagged with satellite-transmitting buoys and tracked for three years. This study reveals that nets that enter the atoll from the northeast travel southwest towards the center of the atoll, and nets in the center can remain ensnared on the same reef for at least three years. This study shows that satellite buoys are a successful approach to tracking derelict net movement, and can inform future debris removal missions. • Nets enter Manawai in the Northwestern Hawaiian Islands from the northeast. • Nets travel southwest towards the center of the atoll. • Nets can remain ensnared on the same reef for at least three years. [ABSTRACT FROM AUTHOR]

Abstract: Debris removal programs are combatting the accumulation of derelict fishing gear and other debris in marine habitats. We analyzed 5years of lobster trap debris removal data in Biscayne National Park, Florida to assess removal efficiency and develop spatially-explicit mapping tools to guide future removals. We generated and validated debris “hot spots” maps that combined remotely-sensed data (i.e. benthic habitat type and bathymetry) with 862 locations of previous debris collection. Our hot spot models spatially depict regions of likely debris accumulation, reducing the search area by 95% (from 332km2 to 18km2) and encompassing 100% of the validation sites. Our analyses indicate removal contractors using sub-surface towed divers enhanced debris recovery. Additionally, the quantity of debris removed did not decrease with increased efforts, suggesting that debris supply in situ exceeds removal efforts. We conclude with the importance of coupling analysis of ongoing debris removal programs with GIS technology to improve removal efforts. [Copyright &y& Elsevier]

The remote and uninhabited Northwestern Hawaiian Islands (NWHI) contain 70% of the shallow water coral reefs in the United States and are regularly exposed to derelict fishing nets. These nets snag on the shallow reefs, damaging or killing benthic communities. However, no data exist to quantify this impact. Here we use a novel application of photogrammetry, Structure-from-Motion (SfM), to calculate benthic cover from mosaic images at net-impact and control sites. Net-impact sites had significantly higher cover of bare substrate, sand, and crustose coralline algae and significantly lower coral and macroalgae cover compared to control sites. These differences were unrelated to net size and fouling. Our study demonstrates the utility of using SfM to efficiently quantify impacts of derelict fishing nets. Revisiting these sites will be essential to document how the reef recovers to further our understanding of the lasting impacts of derelict fishing nets on coral reef habitats. • Coral reefs impacted by derelict fishing nets have higher cover of bare substrate. • Derelict fishing nets cause reductions in coral and macroalgae cover on reefs • Impacts on coral reef communities are unrelated to net size and fouling level. • Structure from Motion imaging efficiently quantifies impacts on benthic communities. [ABSTRACT FROM AUTHOR]