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Marine soft sediments are the most common habitat on earth (Wilson 1991, Dutkiewicz et al. 2015) and are heavily exploited by both commercial and recreational fishers. Demersal fishes, that is those living or feeding on the seafloor, comprise approximately one third of the global fish catch and much of this is caught on soft sediments such as marine sand (AERL 2011, FAO 2016). Soft sediments are the major near-shore and continental shelf environments (Caveen et al. 2012) and almost all marine soft sediments shallower than 1200 m are fished, apart from no-take marine protected areas (MPAs) (Handley et al. 2014).

Marine protected areas are an increasingly common management approach to assist in conserving marine biodiversity (Lubchenco and Grorud-Colvert 2015, White et al. 2017). They use spatial management of a range of human activities by limiting, avoiding or removing anthropogenic activities such as pollution, habitat destruction and fishing (Wells et al. 2016). They are primarily implemented to conserve biodiversity (Wells et al. 2016) but can have potential utility for fisheries management (Botsford et al. 2003, Gladstone 2007). When MPAs are well designed, implemented and human pressures are sufficient1, the abundance, diversity, and length of targeted fish species can increase (Barrett et al. 2007, Edgar and Stuart-Smith 2018). Almost all of the assessments of MPAs effects on fish have, however, been on rocky reefs and coral reefs; rarely have soft sediments been assessed (Caveen et al. 2012).

Despite MPAs being dominated by unvegetated soft sediments, we have very little knowledge on the effects of MPA implementation on the unique communities associated with this habitat (Caveen et al. 2012). MPAs on marine soft sediments are often put in place without knowing if they will protect the fish diversity in this habitat and monitoring of these assemblages, to assess ecological changes, rarely occurs. A good example is the Great Barrier Reef Marine Park in which soft sediments comprise 95% of the seafloor (Caveen et al. 2012), yet there is extremely little information available on the biological effects of management zones on non-reef habitats in the park (McCook et al. 2010). Studies testing the effect of no-take MPAs on fishes are numerous but have largely ignored soft sediments or were limited in nature. Studies on MPA effects that have included marine soft sediment habitats were generally in very shallow water or only

1 _{For example, if there was no or minimal fishing occurring before MPA implementation then there is unlikely to be}

any response in a fish population when fishing is prohibited. In the same way, if there is little or no fishing occurring outside an MPAs borders then differences in fish populations between inside and outside the MPA will not be a result of fishing pressure.

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looked at soft sediment habitats in comparison to nearby rocky reefs, sea grass or coral (e.g. Cappo et al. 2007). Those including sites within hundreds of metres of reef are likely to be sampling a ‘halo’ fish assemblage which may be closer in composition to reef assemblages than those on soft sediments (e.g. Langlois et al. 2005, Schultz et al. 2012). As a result, and as continually highlighted in a number of reviews, the effect of protection on marine soft sediment demersal fish communities is effectively unknown and remains unassessed (Lester et al. 2009, Bloomfield et al. 2012, Caveen et al. 2012, Caveen et al. 2013, Sciberras et al. 2013). Understanding how fish on marine soft sediments respond to MPA implementation appears to be a major gap in our understanding of this worldwide conservation approach.

There continues to be rapid increases in the amount of marine soft sediments under protection globally despite our limited knowledge of MPA efficacy on this habitat. This increase is being driven by exponential growth in the number of MPAs generally (Worm 2017) and also the trend towards more ‘vast’ MPAs (e.g. The Papahānaumokuākea and the Pacific Remote Islands Marine National Monuments) which cover large areas of deep water soft sediments. Soft sediments are often included in MPAs almost accidentally, as they cover areas between other habitats or sites of specific interest, and some are protected in response to CAR (comprehensive, adequate, representative reserves) approaches to spatial planning (Coleman et al. 2013). Beyond their inclusion, seemingly little thought is put into threats to or conservation of these areas, hence the lack of assessment generally or specific hypotheses or goals proposed for these conservation areas. The amount of marine soft sediment habitat being protected in MPAs has far outpaced research on the ecological impacts of MPAs on this habitat. Whether protection of marine soft sediments assemblages can result in the similar outcomes (e.g. more fish and/or larger fish) as can occur on other habitats, such as coral and rocky reefs, has rarely been explored.

The need for data on subtidal marine soft sediments have been identified as a key knowledge gap that is hindering the implementation of effective evidence based MPA management in the Australian state of New South Wales (Brooks et al. 2013). Jervis Bay Marine Park is one of six MPAs in the state. The park zoning came into effect on the 1st of October 2002, however, as in most MPAs, the potential impact of no-take zoning on demersal soft sediment fish abundances and diversity has not been assessed. Jervis Bay

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is dominated by soft sediments and its waters are largely devoid of major human impacts like pollution and modification. Recreational fishing occurs in the majority of Jervis Bay with the exception of its no-take sanctuary zones, where no forms of fishing are permitted. These no-take zones are distributed haphazardly in relation to rocky reefs and seagrasses and replicated across the park. As a result, soft sediments are also well represented in fished and no-take areas. The dominance of soft sediment substrate, its pristine waters and replicated fished and unfished soft sediment areas means that Jervis Bay Marine Park provides a useful opportunity to gauge the impact of fishing and MPA implementation on demersal soft sediment fishes generally.

I hypothesised that the removal of fishing pressure on soft sediments in JBMP no- take zones will result in changes to fish abundance and size of fished species. More specifically, I tested the following three predictions: (1) That abundances of targeted and bycatch species would be greater in no-take zones; (2) that targeted species of fish in no- take zones would be larger than those in fished zones; and (3) there would be greater diversity in no-take zones compared to fished zones. I tested for these predicted effects of no-takes zones multiple times between 2011 and 2015. In relation to time, I predicted that the patterns outlined above would either be stable through time (i.e. indicating effects had already taken place and were stable) or that these patterns would be developing through time. As far as I am aware this is the first long-term study to test for the effects of no-take MPAs on marine soft sediment demersal fish assemblages across multiple years and multiple NTZs.