Review of Methods to Repair and Maintain Lithophilic Fish Spawning Habitat

Abstract

Rocky reefs provide important spawning and refuge habitats for lithophilic spawning fishes. However, many reefs have been lost or severely degraded through anthropogenic effects like dredging, channelization, or sedimentation. Constructed reefs have been used to mitigate these effects in some systems, but these reefs are also subject to degradation which may warrant custodial maintenance. Monitoring and maintenance of natural or constructed spawning reefs are not common practices; therefore, few methodologies have been created to test the effectiveness of such tools. We conducted a literature review to assess available information on maintenance of rocky spawning habitats used by lithophilic fishes. We identified 54 rocky spawning habitat maintenance projects, most of which aimed to improve fish spawning habitats through the addition of spawning substrate (n = 33) or cleaning of substrate (n = 23). In comparison to shallow riverine studies focused on salmonids, we found little information on deep-water reefs, marine reefs, or other fish species. We discuss the possible application of potential spawning habitat cleaning methods from other disciplines (e.g., treasure hunting; archeology) that may provide effective means of reef maintenance that can be used by restoration practitioners.

A structured approach to remediation site assessment: lessons from 15 years of fish spawning habitat creation in the St. Clair‐Detroit River System

“…The SCDRS team discussed the placement and design options candidly and worked to develop consensus. The team recognized that risk of sedimentation remained and therefore contingency plans were discussed, leading to a decision to research maintenance options for sedimented reefs (Baetz et al 2020). Thus, the ordered process to identify constraints and remediation locations (Fig.…”

Assessment of Two Techniques for Remediation of Lacustrine Rocky Reef Spawning Habitat

“…Custodial maintenance (i.e., one form of remediation) of rocky reefs is uncommon, and there is currently no standard methodology in practice. While peer‐reviewed evidence of freshwater rocky reef maintenance is limited (Baetz et al 2020), Johnson et al (2006) attempted to clean small sections of a constructed reef (9 m by 18 m) with scuba divers that used a combination of hand tools and pressurized water; however, the success of this methodology was not documented. Reef maintenance at a small scale could be feasible using teams of scuba divers, though on larger reefs this methodology may not be practical.…”

“…Sediment removal can also be achieved using methods developed for marine archeology. Sediment removal in this field is typically localized, and scuba divers use hand‐held devices, such as air lifts and suction dredges, to remove sedimentation (e.g., Goggin 1960; Cook 2018; Baetz et al 2020). While these methods may be useful on a local scale, hand‐held suction devices may not be practical to rapidly clean large reef areas.…”

“…While these methods may be useful on a local scale, hand‐held suction devices may not be practical to rapidly clean large reef areas. As another alternative, “mailbox” devices and similar designs are used by marine archeologists to redirect or deflect propulsion created by the vessel’s propeller to resuspend fine sediments (Bass 1985; Baetz et al 2020). This method allows the vessel to suspend over an area and direct pressurized water onto a selected area, but this requires a large vessel to produce sufficient propulsion to reach the substrate at depth, and the vessel has limited mobility while the device is being used (Bass 1985).…”

A Before-After Control-Impact Assessment of Gravel Washing as a Lacustrine Spawning Habitat Restoration Method for Smallmouth Bass (Micropterus dolomieu)

“…A common threat to species with similar spawning habitat requirements to smallmouth bass is the accumulation of fine sediments over their preferred substrate, as this can cause increased egg mortality and abandonment of spawning habitats (Baetz et al, 2020). In lotic systems, studies have found jetting or washing substrates has been successful in improving the conditions for substrate spawning fish by reducing fine sediment content near the surface (Meyer et al, 2008;Bašić et al, 2017).…”