Impacts of pollution, fishing pressure, and reef rugosity on resource fish biomass in West Hawaii

Abstract

Human activities and land-use drivers combine in complex ways to affect coral reef health and, in turn, the diversity and abundance of reef fauna. Here we examine the impacts of different marine protected area (MPA) types, and various human and habitat drivers, on resource fish functional groups (i.e., total fish, herbivore, grazer, scraper, and browser biomass) along the 180 km west coast of Hawaii Island. Across survey years from 2008 to 2018, we observed an overall decrease in total fish biomass of 45%, with similar decreases in biomass seen across most fish functional groups. MPAs that prohibited a combination of lay nets, aquarium collection, and spear fishing were most effective in maintaining and/or increasing fish biomass across all functional groups. We also found that pollution, fishing, and habitat drivers all contributed to changes in total fish biomass, where the most negative impact was nitrogen input from land-based sewage disposal. Fish biomass relationships with our study drivers depended on fish functional grouping. For surgeonfish (grazers), changes in biomass linked most strongly to changes in reef rugosity. For parrotfish (scrapers), biomass was better explained by changes in commercial catch where current commercial fishing levels are negatively affecting scraper populations. Our observations suggest that regional management of multiple factors, including habitat, pollution, and fisheries, will benefit resource fish biomass off Hawaii Island.

The coral conservation crisis: interacting local and global stressors reduce reef resiliency and create challenges for conservation solutions

“…For example, a ban on scuba spearfishing and fishing nets increased grazer populations after a year of management. This confirmed that both recreational and commercial fishing are negatively affecting fish populations, but consistent management will aid in recovery [28,66,104]. Additionally, several areas across the Main Hawaiian Islands still support high standing fish stocks, which can be refugia for maintaining fisheries resources [93].…”

“…Coral reef status and resilience can be location-specific due to interactions of localized environmental stressors. For example, in Hawaiʻi, it has been suggested that regional management of multiple factors will benefit fish biomass and coral resistance to elevated temperatures [25][26][27][28]. In the Philippines, reefs have experienced a continued decline in hard coral cover over the past three decades, not solely due to the third global bleaching event (2014-2017) [29].…”

“…Fishing, combined with other localized human drivers, leads to changes in fish biomass and is used as a direct indicator of reef health status and human disturbance level [103]. Pollution, fishing, and habitat drivers led to an overall decrease in 45% of total fish biomass over 10 years (2008-2018) on the west coast of Hawaiʻi [28]; however, regional management of these multiple factors could benefit fish functional groups. For example, a ban on scuba spearfishing and fishing nets increased grazer populations after a year of management.…”

Care, not incarceration: exploring the carcerality of fisheries enforcement and potential decolonial futures in Hawaiʻi

“…The urgency of transforming environmental management arrangements to promote environmental, economic, and social welfare is amplified by the looming climate apocalypse, which will increasingly exacerbate socioeconomic injustices and environmental degradation (Hayhoe et al, 2010;Hsiang, 2010;Keellings and Hern andez Ayala, 2019;Lobell et al, 2011). In addition to perpetuating socioeconomic injustices, current environmental management paradigms have been insufficient in fully addressing the sources of environmental harms and preventing further environmental degradation, as exemplified through continued defaunation, fisheries stock depletion, and habitat loss (Coleman, 2004;Dirzo et al, 2014;Foo et al, 2021;McCauley et al, 2015;Puigdef abregas, 1998;Young et al, 2016). Furthermore, despite evidence demonstrating the efficacy of decentralizing environmental management schemes, governing powers remain centralized, thus disenfranchising communities and diminishing the viability of management arrangements (Aswani et al, 2018;Fitzsimmons, 1998;Marshall, 2008;Olsson et al, 2004;Vaughan and Caldwell, 2015).…”

“…A consequence of the history of Hawaiʻi, the islands depend on imports for over 80% of locally consumed foods, making the islands remarkably food insecure and therein vulnerable to market fluctuations and impacts from extreme climate events (Akutagawa et al, 2012;Lipper et al, 2014;Loke and Leung, 2013). And yet, as minimal as they are, current local food systems place considerable burden on the ʻ aina (land, that which feeds), as exemplified by depleting fish stocks from pollution and overfishing (Foo et al, 2021;Friedlander and Parrish, 1997). As a case of investigating the holistic efficacy of environmental governance paradigms, this paper focuses on fisheries management in Hawaiʻi.…”